forward - The Art of Diesel

FORWARD
Before digging in, I need to give credit to those who have gone before me. I’m far from being the first to install a
small diesel engine into a full-sized American truck. Much of what I’ve done has been done many times before –
often by people much smarter and more knowledgeable about diesel engines than I am.
Here are a few important people who were helpful and deserve credit:
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My wife, Catherine, and my children who have to put up with the very driven, impatient, eccentric,
individual that I am. I love you all and am looking for a path to spend more time with my family!
All the users in the Isuzu 4BD1T forum at www.4btswaps.com, especially:
o Rod Brace, aka love-horsepower, who has also converted several vehicles to diesel, including at
least two Suburbans. I believe he was one of the first to maintain four wheel drive with an Isuzu
engine swap. Rod provided me with useful information, allowing a tall engine to coexist with a
nearly stock independent front suspension system.
o Tim Brotzke, aka DieselTim, who sells adapters and convinced me to go the NV4500 route –
probably the best decision made in this conversion. Today he is working with Rod Brace on
adapters that mate the Isuzu engines with Dodge automatic transmissions. Options for other
manufacturers are coming soon. Check out his website here: http://www.4bdconversions.com
o Dougal Hiscock, the “Isuzu Diesel Innkeeper,” a mechanical engineer from New Zealand, who
helped me in my turbo selection process. His homebrewed hybrid turbo experience was an
excellent data point for me to build on. His ongoing efforts dispel misconceptions and continue
to further everybody’s understanding of how turbochargers interact with diesel engines.
o Carcrafter22, who is well-known for his compound turbo, 500 hp 4BD1T that was installed in a
60s vintage Ford F100 (check out this video http://youtu.be/ws3D62pBI0A ). I’m not sure how
long the engine lasted, but it was inspiring to see how far a 3.9 liter Isuzu engine could be
pushed.
Friends and family who proof-read and critiqued my writing. Trying to polish the odd ramblings of a mad
man is no small feat. This includes:
o Marek Marasch
o Jefre Cockerham
o Jack O’ Alltrades
Note that I’m a radical, hard-core, (small L) libertarian. I will express a number of controversial opinions in this
book. I can rant a bit, at times. Please note that these opinions are mine and mine alone. They shouldn’t be
attributed to any of the nice people above. Their tolerance for me and my views shouldn’t be misread as an
automatic endorsement!
It wasn’t too many decades ago when Americans were people who wouldn’t think twice about tearing into cars,
modifying them, and improvising to create better machines. These people didn’t make a big deal out of doing
these things. In those days, engineers were fast to move forward with designs and hardware prototypes. They
didn’t fear failure, for that was an important part of the learning experience. These engineers developed deep
knowledge and a feel for what they were doing through real experience. Their passions and ambitions weren’t
crushed by the realities of a modern business atmosphere where failure is to be avoided at all costs. As a result,
they developed the art of design.
We often hear about the college graduate who continues to live his life in his parents’ basement playing video
games. Many Americans today have been lulled into stupidity by school systems that indoctrinate, rather than
teach. They’ve also been lulled into laziness and apathy by an infrastructure fed by the government that promises
to give them everything they need. Humans are social creatures, and generally live up to the expectations that
have been revealed to them. As I write, this culture is working to ruin yet another generation with silly ideas about
what is “normal,” accompanied by low expectations.
Against the odds, there has been a resurgence of people willing to roll up their sleeves, cut metal, “get their hands
dirty,” and actually do real things. This is a positive development and a natural reaction to our current economic
woes. It would be amplified if we didn’t have an interventionist federal government and a compliant Federal
Reserve cooperating to stimulate the “business cycle” and increase the population’s misery. In a truly free (nonKeynesian) economy, this wave of ingenuity is exactly how a market would build a strong foundation and recover.
This is the source of what used to be known as good ol’ American know-how – a term with origins from the days
when the USA had a (relatively) free market and more liberty. It wasn’t some genetic quality of Americans, as
most of their genetics didn’t originate on this continent. It came about because free markets inherently reward
hard work, ingenuity, and service to fellow human beings. Today free markets have been destroyed by
government tinkering, and less productive behaviors receive positive reinforcement.
Regardless of these influences, a positive movement is growing. Outstanding humans refuse to be trampled, and
they always seek something better. This shows up in the maker/hacker movement, as well as in forums like
4BTswaps.com where scores of people worldwide are dropping a wide variety of diesel engines into almost any
platform you can imagine. It also shows up in the journalistic approach of alternative media sources spreading the
truth about the reality that we live in. I believe that technology is enabling this movement by:
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Making it very easy for people to find and communicate with like-minded people from all over the world;
Allowing for wikis, forums, and videos where people can learn in a natural, social fashion – including from
each other’s mistakes;
Easy access to technical information on engines, vehicles, and gadgets – as many manufacturers post
manuals online, and many users scan manuals to post and share;
A thriving, international marketplace for tools, vehicles, engines, components, and other gadgets;
The continued development of consumer-level 3D “printing” machines, combined with global file sharing
capabilities;
The realization of a worldwide market where individuals can share with, buy from, and sell to other
individuals anywhere in the world.
My point in writing this book isn’t to share some great, innovative, new approach to doing something, or even to
show off my own expertise. In fact, I’m not really an expert in any single subject. I consider myself to be a
generalist who is interested in a large number of subjects. My intent is to bring together information from my
project in a single straightforward volume. Most all of the information I’ll provide is available on sources such as
4BTswaps.com and IH8mud.com, but the reader may spend weeks or months digging for the nuggets of
information they need for their project. At the beginning, the reader might not even know what nuggets of
information they should be looking for. Even with the guidance of a book such as this, a smart builder will join
these forums, learn from them, and contribute what they can.
In this book’s technical chapters, you will find a discussion that is often more about what and why I did, rather than
exhaustive detail on how I did it. I will discuss:
1.
2.
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The options I faced and the decisions I made. Taking a logical approach can save some serious headaches!
What I wound up doing, and some of the more useful, hard-to-find technical secrets of the conversion.
What I would do differently if I did it over again. There’s always room to do a better job, and I want you
to gain from my experience.
Sprinkled throughout the book you will find my personal philosophy – something which is inseparable from my
reasons for building this machine.
I hope you enjoy this book! Please contact me directly with any feedback or questions you have by sending emails
to [email protected]. Also, be sure to visit my libertarian gearhead blog at www.theartofdiesel.com,
where I will continue to provide updates on my projects and my view of world events.
CHAPTER ONE: WHY WOULD ANYBODY DO THIS?
I installed a 4-cylinder turbodiesel engine into a 1999 Suburban K1500. I’ve been driving it that way for over a
year, improving on the installation as I go. Quite a few people have been impressed by how the installation turned
out and the excellent fuel economy that resulted. Some have said that the installation looks better than the stock
5.7, but I think they are exaggerating a bit. With an NV4500 5-speed manual, stock 3.42 gears, and my current tire
size, the engine is turning only 1900 rpm at 70 mph. This is the rpm where this engine produces its peak torque
and fuel economy. The result is a drivable, reliable family hauler that gets 26 mpg on the highway.
Many people – even fellow engineers – think I’m crazy and wonder why I would ever do such a thing. In this first
chapter, I discuss why I undertook this task, rather than buying one of a number of existing vehicles on the market.
This entire book is about the options I faced, the decisions that were made along the way, how things turned out,
and what I’d do differently if I started over.
NEEDED: A FAMILY HAULER FOR THE FLEET
Before this adventure began, we had three very good, functional vehicles, all of which were paid for. Two of them
were already factory-equipped with diesel engines, as I had already caught the diesel bug. My wife and I are
philosophically against debt – because it increases fragility and can be a form of slavery. So, making payments isn’t
something we enjoy and we quickly pay our loans off.
We didn’t have a large vehicle, and I wanted to have a better family hauler. There are only four of us, but we have
two good-sized German Shepherd Dogs that like to go places with us. Because we refuse to expose our children to
the touch of the TSA’s filthy blue gloves, our family vacations are always road trips. We also maintain a homestead
with chickens, rabbits, bees, and gardens. As these interests grew, it became obvious that more hauling
capabilities were needed. We wanted a vehicle that could haul items like lumber, bags of feed, furniture, and
equipment without having to pull a trailer.
Before building my diesel Suburban, our primary family hauler was my wife’s 2005 Jeep Liberty CRD. This was the
first diesel-powered vehicle we owned. We purchased it with the intent to drive a reasonably sized SUV with good
efficiency. While delivering fuel economy in the mid-20s, the 2.8 liter VM Motori 4-cylinder engine provides
snappy response – making the Liberty fun to drive. This is my wife’s daily driver, and she really enjoys it. When we
bought it, she was immediately comfortable with its compact dimensions, which are similar to the Cherokee XJ
that it replaced. However, even with the use of a large, hitch-mounted cargo box, this vehicle really doesn’t give
my family enough space when we need to haul dogs, large objects, et cetera.
When we bought the CRD, we kept the XJ. Its trade-in value was low, and we decided to keep it as a spare vehicle
that could be used on snowy days. It was still in good shape and had shiny red paint, but the fuel economy was
terrible for such a small, lightweight vehicle. It was equipped with the high output version of the 4.0 inline six
cylinder, and never got more than 17 mpg on the highway – very similar to the Suburban’s stock fuel economy
with a 5.7 liter V-8. The 4.0 was quick, but not quick enough to justify what it cost to drive.
After we bought the CRD and realized that modern diesels were not just extremely efficient but also fun, it wasn’t
long before I started questioning my Saab 9-3’s fuel economy, which was only in the upper 20s. I sold it and
bought a beat up 2001 Volkswagen Jetta TDI with 185,000 miles on it – knowing these engines’ reputation for
longevity. When I bought the that VW, it had reasonable acceleration and was easily the most efficient vehicle I’ve
ever owned (including a couple motorcycles). The Jetta TDI delivers me to and from work in comfort, with a
reliable efficiency of 45 mpg. A re-flash of the ECU from Kerma TDI really woke it up, making it quite a bit sportier
and fun to drive, with absolutely no effect on fuel economy (provided that I don’t “floor it” all the time). This car
now has over 250,000 miles on it, and is continuing to deliver the same efficient, reliable transportation. The
experience with our two diesel vehicles inspired me to see what else I could do with a diesel engine.
I had read about many diesel swaps through the forums on 4BTswaps.com. I realized that I could build a goodsized hauler that might have a low horsepower figure, but would be more than adequate for hauling my family,
dogs, and gear around.
ECONOMICS AND FUEL ECONOMY
Not only did I need a decent-sized family hauler, I wanted one that was efficient. Fuel prices had spiked in the
preceding years, hurting the family budget. This wasn’t caused nearly as much by shortages or excessive profits as
the corporate media would have us think. If one looks at the price of fuel in terms of a hard asset such as silver,
the value of a gallon hasn’t changed as dramatically as we’ve been led to believe. The Federal Reserve’s inflation
of the dollar has devalued our currency, causing energy prices to rise nominally, even as our incomes remain
stagnant. The corporate media and the government insist that price inflation has been negligible for the last six
years – showing either deceit or a complete disconnect from reality. People are too willing to believe the
government’s Core Price Index (CPI) figures, which are nothing more than propaganda. Simply paying attention to
the rising costs of living should make this obvious to anyone, especially when food and energy are included. CPI
figures conveniently ignore these factors, even as the United States government and the Federal Reserve pursue
inflationary monetary policies.
The bottom line is that fuel has the potential to become very expensive. Even if energy costs stayed exactly as
they are today, it is already very expensive to operate a large, inefficient vehicle. This is exactly why large vehicles
equipped with inefficient gasoline engines can be found at bargain prices today.
From my previous experience with diesel vehicles, I knew that a diesel engine could easily produce 50% better fuel
economy than a gasoline powered version in the same application.
FUN TO DRIVE
Some will say that diesels are slow, but that probably means they haven’t driven one lately! Engines with wide
torque curves that kick in at low and mid-range rpms will deliver more acceleration than engines that have high
peak horsepower ratings at high revs. When gassers achieve their claimed peak horsepower figures, they have to
upshift immediately, and start the revving process again. This is why my wife’s Jeep Liberty CRD has a better 0-60
time than the 3.7 liter gasser version of the same vehicle. It may only have 160 horsepower, compared to the
gasser’s 215, but the diesel’s 295 lb-ft of torque at 1800 rpm makes a huge difference 1. All of that torque makes a
diesel powered vehicle very responsive and fun to drive. I also like the distinctive, clattering sound combined with
the sound of a spooling turbo and a whiff of diesel exhaust. To me, it sounds and smells like efficiency!
FUEL OPTIONS
1
Mike McGlothlin Buying a Used Jeep Liberty CRD; Diesel Power Magazine, April 2011.
http://www.dieselpowermag.com/features/1104dp_buying_a_used_jeep_liberty_crd/
Diesel engines can be run on fuels other than petroleum-based diesel fuel. When Rudolf Diesel displayed his
engine at the World Exhibition in the year 1900, it was running on peanut oil. Part of the idea behind his engine
was that farmers could grow their own fuel. Regardless of political and economic mechanics of how it happened, a
petroleum-based diesel fuel (developed later) became the primary fuel for diesel engines 2. The basic function of a
diesel engine has not changed, but modern diesels are electronically controlled and carefully tuned to get the most
power, highest efficiency, longest life, and lowest emissions from the petroleum diesel fuel standard. Modern
injection pumps are designed for the viscosity of the petroleum product, and are rather expensive to replace.
Unfortunately, this means that only the courageous will run these engines on straight vegetable oil like Dr. Diesel
did. More careful owners may set up a biodiesel reactor to convert the vegetable oil they collect, but this can be a
fairly complex process that most won’t pursue.
For this project, I chose an older mechanically-injected diesel engine. It’s a simpler system to install, requiring no
electronics and, strictly speaking, only the starter motor needs to be connected for the engine to function (even
the glow plugs aren’t really needed, unless it is very cold). These simpler engines are less fussy about what fuel
they are fed. So, biodiesel and even straight vegetable oil are options that would have no ill effects on this
powerplant.
Dwaine Halberg and Dan Sackett of Saguaro Materials Research are working on systems with the goal of enabling
consumers to easily create a gallon or two of their own algae-based biodiesel daily, without requiring a huge field
or pond for growing the needed biomass. If the right algae species are used and the processing is developed
properly, the fuel will be useable even in the more complex modern diesel engines 3.
In summary, the inherent flexibility of diesel engines (especially the less sophisticated ones) allows for a variety of
fuel options, including biofuels. Gasoline engines can also be run on biofuels, but the most common biofuel used is
ethanol. Ethanol is typically made from corn and its use for fuel is the result of lobbyist influence and the
government’s unconstitutional hobby of endless economic tinkering. Ethanol would never have emerged as a fuel
in a free market economy, as actual production costs are high, energy density is low, and the stuff is hygroscopic.
The latter is especially negative, as it limits how long ethanol can be stored before being used as fuel. If one is truly
interested in biofuels for gasoline engines, they should take a close look at butanol – which can be made from any
cellulose fiber, including grass clippings, corn stalks, yard waste, or almost any source of disposable biomass.
WHY NOT AN EXISTING DIESEL?
Seven years ago, I was developing an interest in diesel engines for their power and efficiency. I considered how
nice it would be to have a larger vehicle that was fuel efficient. However, I noticed that the vehicle I wanted was
mysteriously absent from the marketplace. I was tracking a number of developments and options for a few years
before I embarked on this project.
The first possible candidate was the early Mercedes Sprinters. These are exceptionally large, yet lightweight vans
that were often sold in the USA with Freightliner or Dodge badges on them. In the early 2000s these vans were
sold primarily with an OM612 2.7 liter, 5-cylinder turbo diesel. With this engine, users were reporting fuel
2
Biodiesel of Las Vegas The History of Biodiesel. http://www.biodieseloflasvegas.com/biodiesel-history.aspx
(accessed December 2013).
3
Dwaine Halberg, Dan Sackett Declare Your Independence with Ernest Hancock, May 2nd, 2013.
http://saguaromaterials.com/radio_interview.htm
economy typically in the range of 23 to 27 mpg. Some were delivered as passenger vans, but the most commonly
available units were cargo vans. At the time that I started my project, a used, high-mileage Sprinter in good
condition was going to be a $15k proposition. These were mostly cargo vans, so one of these would require a 70’s
style homebrewed conversion (minus the shag carpet, water bed, round windows, and chromed control pedals
shaped like feet). These conversions wouldn’t be cheap, requiring the installation of windows, seats, and
upholstery. This would result in a very unusual family vehicle with terrific internal volume. One could probably
haul kids, dogs, and sheets of plywood simultaneously, if desired. However, I wanted to replace the 4x4 Cherokee
XJ; meaning that my conversion would have to be a four wheel drive vehicle for use on snowy days. Some
Sprinters were manufactured with four wheel drive, but until recently they were not available in the USA. I found
companies that were performing four wheel drive conversions on these vehicles, but it would cost in the range of
$23,5004 to $28,0005. This would result in an exceptionally large, efficient, 4x4 vehicle, but it would cost upwards
of $40,000 – a level of debt that I was unwilling to accept. If I was ready to live without four wheel drive, the total
cost would be in the upper teens, but I didn’t feel this was an option.
Late 90s Dodge 2500 Ram pickups are reported to get fuel economy in the mid to upper 20s when equipped with
the Cummins 5.9 liter, 6-cylinder turbodiesel (known as a 6BT), with the right gear ratio. Quad cabs were available
in these years, but these weren’t proper four-door pickups and the back seats offer little legroom. Though they
offer great cargo capacity, they aren’t great family haulers. After those years, the American truck manufacturers
got into horsepower and torque wars, and fuel economy figures dropped as a result. Those vehicles are designed
to pull houses down the road at highway speeds, and they simply do not meet my efficiency goals.
Another option that was “imminent” for a number of years was a truck called the PikUp built by Mahindra and
Mahindra in India. Mahindra is known in the USA primarily for the tractors which are sold here. Worldwide, they
are known for building licensed, diesel-powered Willy’s Jeep knockoffs. Mahindra has expanded their line in
recent years to build some more modern SUVs and pickups, though none of them have been available in the US
market. Mahindra was working with Global Vehicles to import an Americanized (EPA-compliant) version of their
mid-sized 2 and 4-door pickups. Powered by a 2.2 liter turbodiesel, these were expected to get 30 mpg with a
hauling capacity of over a ton. Every six months the new updates said that they’d have them on showroom floors
in another six months. They had already sold a number of dealerships around the country, and the owners of
those were understandably eager to get them in stock. Once the vehicles finally passed EPA certification,
Mahindra failed to deliver any to Global Vehicles. I’m fuzzy on the details of why or what occurred after that, but
there was a lawsuit and everything fell apart. I would have considered buying a 4-door, four wheel drive version of
this pickup, but they never made it to our shores.
Back in 2006, other options were being considered by American manufacturers that would have provided my
desired high-efficiency family hauler. The Big Three were each developing diesel engines for ½ ton trucks. Each
was predicted to get fuel economy in the upper 20s, or even 30 mpg in full-sized pickups. However, all of those
efforts were shut down when hard times hit in 2007 and 2008. Two of the three companies required government
bailouts to stay in business, and the third was also forced to make tough choices. So, my hopes for a ready-made,
efficient family hauler were dashed.
4
White Feather 4x4 Conversions Sprinter 4x4 and 6x6 FAQs http://whitefeather4x4conversions.com/faqs/
(accessed December 2013)
5
The Sprinter Store Sprinter 4x4 http://sprinterstore.com/sprinter_4x4.htm (accessed December 2013)
Some truly fantastic “options” that might be considered by somebody without any budget constraints include the
Legacy Powerwagon vehicles (www.legacypowerwagon.com) – which are available with a 4BT 3.9 liter 4-cylinder
Cummins turbodiesel and an NV4500 transmission (interesting formula!). As cool as they are, I can’t imagine that I
would ever spend $120,000 on a vehicle. These make a Sprinter 4x4 look very inexpensive.
Today, government-imposed CAFE (Corporate Average Fuel Economy) standards are forcing a number of
manufacturers to come up with gas-powered full-sized pickups that have highway fuel economy figures that are
solidly in the 20s. Some are hybrids – which I would never consider because of both the initial expense and the
long-term complexity. A number of pickups deliver efficiency in the 20s even without such exotic drivetrains, built
by Toyota, Nissan, and Ram (the brand previously known as Dodge Trucks). The Ram is interesting, as the most
efficient gasser version is a 1500 powered by a 3.6 liter gasoline engine coupled with an eight-speed transmission.
All of these vehicles are two wheel drive versions. They weren’t on the option list, as they weren’t available when I
started my project. Even if they were, they are all much more expensive than the combined cost of my Suburban
and the conversion.
As 2014 approaches, some ½ ton diesel trucks are finally emerging. Ram will be offering a 3.0 liter Ecodiesel V-6
with an eight-speed Torqueflite. MotorTrend just completed a test showing that this VM Motori-equipped
machine can get 28 mpg in 2wd trim 6. In 2015 the new Nissan Titan will arrive with a 5.0 liter V8 diesel built by
Cummins, but I doubt the fuel economy of this machine will be quite as high. I’m not one to run out and buy a new
vehicle, though, and the most basic Rams have MSRPs in the $25,000 range. Adding a diesel powerplant of any
sort certainly drives the price closer to $30,000 or beyond. Again, even if these were available when I started this
project, I probably would have still pursued an effort to build my economic family hauler.
SURVIVAL
Some say that survivalists are weird – members of the lunatic fringe. But what’s wrong with being prepared? A
“zombie apocalypse,” a nuclear war, or a complete societal collapse isn’t necessary for some basic preparations to
be useful. Being prepared can help an individual and their family weather events that happen to scores of people
every year, such as losing the local power grid in an ice storm, having a road washed out in a flood, or losing a job.
People who are prepared will also be more capable of taking care of their friends when they are in need. Having
an efficient 4x4 could really be helpful for hauling people and supplies in a range of situations including natural
disasters. A vehicle like my Suburban would make an ideal “bugout” vehicle if a family needs to evacuate because
something nasty is happening in the local area. If there isn’t easy access to fuel or other supplies, this vehicle has a
40 gallon tank, and a potential range of over 1,000 miles. With further modifications, it could also become a
portable power generator.
Considering less likely scenarios, I should point out that our entire modern culture is very vulnerable to high power
microwaves and electromagnetic pulses (EMPs). EMPs are often associated with nuclear explosions, but it is
possible to create an EMP that disables solid state electronics without wiping out a city or creating radioactive
fallout. It is also possible to create very similar effects with high power microwaves in a limited area. Unlike in the
movies, electronics do not need to be functioning when exposed to these phenomena to be turned into useless
garbage. Because most modern vehicles rely on solid state electronics for their engine and transmission controls,
their owners are likely to be traveling on foot after such an attack. My Suburban features a standard transmission
6
MotorTrend 2014 Ram 1500 EcoDiesel Gets 28 MPG Highway in Real MPG Testing, 18 Nov 2013.
http://wot.motortrend.com/1311_2014_ram_1500_ecodiesel_gets_28_mpg_highway_in_real_mpg_testing.html
and a mechanically-injected diesel engine, so it requires no solid state electronics to be driven, and could wind up
being the only functioning vehicle around (though I wouldn’t have a speedometer, tachometer, or radios, and my
transfer case would have to remain in its current mode). This is an unlikely scenario, but it is a side benefit to
having one of the simplest drivetrains on the road today.
LIBERTY
Finally, the number one reason for doing this: It’s all about liberty! No, I’m not about to go rambling on about my
wife’s Jeep, again; I’m talking about freedom.
I believe that God created humanity in His image, endowing us with souls and the innumerable rights that
accompany them. If you don’t believe in God, you could attribute the same philosophy to natural law. Many
would go deep into the founders of the United States and the Constitution here, but neither the signing of a
document nor the creation of a republic created our rights. The US Constitution simply recognized what was
already true.
As a human being, you are an amazing creature with high potential and unique capabilities. No human being owns
you, and you shouldn’t be enslaved by other people. You should also avoid allowing yourself to be enslaved by
drugs, alcohol, debt, gambling, mainstream media, or any of the common modern addictions. It’s your job to live
free, and the actions you take will determine whether you succeed. You were born free, but nobody else can keep
you that way; it is a product of the decisions you make in life.
MINIMIZING DEBT
I minimized debt on this effort. I took out a small loan for the purchase of the stock Suburban. I was able to keep
the loan small because people were dumping these inefficient machines. I did nearly all of the work myself and
paid for parts as I went. It took 18 months to build this machine, but I had the Suburban loan paid off in just a few
months. When this machine was drivable, I truly owned it in every sense of the word. There is a strong sense of
satisfaction when you finish a project, and you feel a stronger sense of pride in something that you made. In fact, I
never feel that I truly own something that I haven’t modified.
Some bonuses and overtime pay helped make this possible, but I think that many people could manage their
priorities and resources carefully enough to manage a similar feat. A few recommendations follow for keeping
costs manageable:
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Don’t rush the process. It took me about 18 months before this vehicle was ready for a cross-country trip.
Consider modifying a vehicle that you already own, but don’t use your daily driver. This vehicle will be out
of commission for a number of months!
Try to do things right the first time. Research what you are doing and learn from the mistakes of others. I
repeated too many efforts on this project. Trying to cut a corner or take a shortcut can very quickly
become a waste of precious time and money.
Work toward making the vehicle drivable, first. When you can hear that engine purring and take it out on
the road for the first time, you’ll find new inspiration. After that, you can steadily build up things that are
nice to have, like functioning air conditioning, an accurate tachometer, pods and gauges for performance
tuning, upgraded suspension components, and power upgrades.
Build up an account for buying parts as you go. Maintain a reserve, so that you can jump on bargains
when you find them.
●
Pick up skills and tools along the way: both have inherent value. If you learn how to weld on this type of
project, you will open options that I didn’t have and will always have that valuable skill.
● Sell components you don’t need in order to buy ones that you do. This includes the stock engine and
transmission from the vehicle.
On that last point: Don’t be sentimental about the original parts. I still have a stack of original Suburban and diesel
engine parts in my barn that weren’t needed for the project. They only serve to collect dust and use precious
space. I will get these sold soon, so I can do more upgrades!
I chose to go against convention on this project in every way that I could. Not simply because I was born a
contrarian, but because the modern approach to vehicle ownership is simply wrong. People sign up for multiple
years of debt, and most wouldn’t dare modify their vehicles by doing anything irreversible. Most have adopted an
authoritarian philosophy that only experts should modify or repair anything. This same approach extends to other
aspects of our lives, including house repairs, healthcare, and our children’s education. The culture tells us that
somebody else always knows what’s best for us, and I disagree! We fear messing things up, and this is especially
true when we are still making payments. We let somebody else take responsibility, because we doubt our own
capabilities and because somebody is ready to take it from us. Then we pay the price by allowing our children to
be indoctrinated by an authoritarian culture and selling ourselves into a lifetime of debt. We accept heavy debts
to drive a status symbol that will be another boring beater by the time it’s paid for. When that happens, we trade
it in and sell ourselves right back into slavery. It’s up to each of us to break that cycle, say no to silly status
symbols, and assert our status as individuals.
There were conventional-thinking naysayers who thought that I was violating something sacred about the
manufacturer’s intent for this vehicle. You would be surprised how many naysayers were engineers and/or
extended family members: the very people that you’d expect to be excited and supportive. They behaved as
though my property rights were somehow void and that GM could somehow dictate the vehicle’s configuration.
GM sold it in 1999 and quit worrying about it as soon as the warranty expired. Today this is my vehicle. I own it
outright. I have the right to decide what should be done with it. I refuse to bow to the pressures of normalcy. By
modifying this vehicle I asserted my own free will and independence. Yes, it’s true, Ayn Rand would be proud of
my attitude in this regard.
If you choose to undertake a similar effort, you’ll be doing the same. In the end, you will not only have the
opportunity to show off something that is truly unique, I am convinced that you will also build up your personal
self-reliance and liberty in the process.
GENERAL DISCLAIMER
I need to make one more important point, not just because we live in a litigious environment, but because I seek to
be intellectually consistent. As a libertarian, I believe that habitually asking permission is a type of sickness. But,
before you embark on any vehicle conversion, you should check on your state and local laws to see if this will
cause any problems for you. There could be very real, practical issues if you live in a state that performs emissions
checks or otherwise frowns upon this type of vehicle modification. You should take the time to research and
inform yourself before starting on such an effort. You will own all of your results, whether they are positive or
negative. I will not take responsibility for your actions or the consequences you may suffer.
CHAPTER TWO: ENGINE SELECTION AND PURCHASING
Before I even found my Suburban, I selected my engine, purchased it, and brought it home. Picking the right
engine is a matter of opinion and priorities, and I will certainly share mine here.
To be clear: everything I’m about to say about engine selection applies to relatively large non-commercial vehicles
like my 1999 Suburban K1500, which has a stock curb weight of around 5,300 lbs and a sizeable engine
compartment – precisely the same engine compartment as any GMT400 pickup. The GMT400 pickup model years
were from 1988 to 1998, while the Suburban and Tahoe GMT400s continued for 1999. If you are looking at a
diesel engine for use in a vehicle that is another size, you will have to examine the size, weight, and capabilities of
any power plant you consider. You will then need to compare these with the weight of the vehicle and consider its
intended purpose. If you want a hot rod, you’ll probably want to go with a more powerful, torquey engine. If you
are going for fuel economy, you’ll want to use the smallest, most efficient engine you can get away with – short of
making the vehicle dangerously slow or undrivable. As I mentioned before, it can be very helpful to find others
who have finished similar projects, so that they can advise you on what worked and what they would do differently
if they did it again.
I spent a number of years looking at the 4BTswaps forums before I took any action of my own. This site is probably
the best source of information on diesel swaps available anywhere. The site gets its name from the Cummins 4BT,
which is a 3.9 liter, 4-cylinder turbodiesel – much like the Isuzu 4BD1T that I chose for my conversion. The
Cummins 4BT has become very popular for swaps, as it provides a nice balance of torque, power, weight, and
efficiency. It is very similar to the Cummins 6BT, which is an inline 6-cylinder, 5.9 liter turbodiesel used in Dodge
pickups – minus two of the cylinders. The 4BTs are often found in step vans used for delivering potato chips and
baked goods to stock store shelves.
If you wish to learn about swaps that use other engines, don’t be put off by the name of the 4BTswaps website. It
covers conversions using the larger Cummins 6BT, the smaller B3.3, and engines made by Isuzu, Mercedes,
Mitsubishi, Volkswagen, Toyota, GM, Detroit, Perkins, Caterpillar, Deutz, Ford, and others. The Buildup Showcase
portion of the forum contains almost 800 discussion threads, covering a wide variety of engine and vehicle
combinations. Spending some time searching through the forums is a good idea, as you may find that somebody
else has already performed the swap you are considering, or something similar. When detail is shared in the
forums, you will learn much about the challenges you are likely to encounter and the solutions that have been
found. You will also obtain real-world examples of efficiency, drivability, and performance that have been
achieved.
From reading through these forums, I knew that turbodiesel engines of the Cummins 4BT’s class would be
adequate for mid- and full-sized pickups. I scoured the forums looking for the power plants providing the best fuel
economy and performance in full-sized pickups and large SUVs, first. Several power plants are worth
consideration, but I will concentrate on why I chose the Isuzu 4BD1T.
FUEL ECONOMY
The main purpose in this effort was to achieve the best fuel economy I could with a full-sized family hauler. I
needed an engine with the demonstrated capabilities of pulling around a full-sized truck while providing good fuel
efficiency. I was hunting around for conversions that met these goals. I found quite a few examples where people
weren’t happy with their resulting fuel economy, but I believe this was often due to non-optimal gearing and/or
transmission choices. I was shocked when I stumbled across the IsuzuDieselSwapper.com website (a site that no
longer exists) and found that their Silverado conversion achieved 32 mpg on the highway using a 3.9 liter Isuzu
4BD1T. Further research showed that these engines could be modified as easily as the Cummins 3.9 liter engines
to increase their output. Sold! This was the engine that I would use for my conversion.
The Isuzu section of the forums on 4BTswaps.com primarily discusses the 4BD1T and the 4BD2TC. The 4BD1T is a
3.9 liter, 4 cylinder turbodiesel engine that is normally found in 1986-1991 Isuzu trucks in the US. These trucks are
often re-badged as Chevy and GMC trucks. These are medium-duty cab-over trucks that are often fitted with large
cargo boxes. The 4BD1T is a direct injection engine, meaning that a high-pressure pump pushes fuel through the
injectors into the engine during each combustion event. The 4BD2T is found in the NPR trucks from 1992 to 1998.
It is based on the same 4BD1 block, but features an intercooler and an indirect-injection fuel delivery system. The
4BD2T provides a small increase in stock horsepower over the 4BD1T. The experience reflected in the forums has
been that the direct injection 4BD1T offers better fuel economy – so I didn’t consider the newer engine. I would
start with the most efficient base available.
ADEQUATE PERFORMANCE
Unless a vehicle will be used as a hardcore tow rig for pulling 5th wheel campers, car haulers, and other extremely
heavy objects at highways speeds, the four cylinder turbodiesels are certainly adequate. After the swaps, the
resulting vehicles aren’t likely to become dragsters, but these engines will provide enough power for a full-sized
pickup or similar vehicle (perhaps with a relatively light trailer) to be driven at highway speeds with no complaints
or issues. I must underscore the qualification that these are turbodiesels – not the naturally-aspirated versions of
these power plants. Diesels without turbochargers should be avoided for on-road use. Choosing an oversized,
naturally-aspirated engine to make up for the lack of a turbo will result in a very heavy setup and lower efficiency
overall. If you are concerned that you might put the time and money into performing a swap only to find that you
are unhappy with the performance, keep in mind that most of these engines will readily accept upgrades to their
air and fuel delivery systems. As an example, I was unhappy with the 4BD1T’s stock turbo at low rpms, so I
upgraded to a better turbo and added an intercooler. This process will be discussed in detail in chapter ten.
I still see a number of late 80s NPR trucks on the road – a testament to the durability and longevity of the 4BD1T
power plant. These engines are only rated at around 121 horsepower, but have a fairly healthy 231 ft-lb of torque.
Torque is fairly flat, peaking at a mere 1900 rpm – which is the same rpm where the specific efficiency is
maximized7. CarCrafter22 built a 4BD1T that used a stock block with stiffer valve springs for high rpm use, an
upgraded Scheid injection pump, a custom exhaust manifold, and a compound turbo setup. This engine put out
some obscene boost levels and he claimed it produced 500 hp 8.
I wasn’t going to go crazy with my 4BD1T, but I knew it was capable of moving a reasonably-sized family hauler
around. In normal use, these engines power a medium-duty Isuzu NPR truck with a gross vehicle weight of just
under 15,000 lbs. I also knew that it possessed the potential for upgrades as needed, so I considered the 4BD1T to
be a good option.
VIBRATION
Many diesels, including the Cummins 4BT, are known for excessive noise and vibration. Many on the forums had
stated that the Isuzu 4BD1T was a smoother, more “automotive” engine 9. It wouldn’t do to make my family deaf
or shake them too much when we are going down the road, so this was in the Isuzu’s favor over the Cummins. I
haven’t compared the Cummins and the Isuzu side-by-side, so I haven’t verified whether this is true.
MAINTAINABILITY AND PARTS AVAILABILITY
Because there are quite a few Isuzu NPR trucks on the road, part availability wasn’t expected to be an issue. Napa
Auto Parts carries parts and quite a few can be found on eBay. I’ve also had good luck when contacting
nprparts.com for parts I need. This site is run by Bellamy-Strickland Isuzu in Georgia, and my parts always arrive
very quickly.
The 4BD1T’s piston liners are pressed into the block, so I knew that an overhaul would actually be quite easy, if
necessary. These engines have been known to go several hundred thousand miles in the NPR trucks, and would
probably last longer in a lighter vehicle – provided that one doesn’t get too crazy with performance upgrades.
PRICE
7
Dougal Hiscock, thread entry: Official 4BD1T Power/Torque Curves, 4BT Swaps, 20 Feb 2012.
http://www.4btswaps.com/forum/showthread.php?22203-Official-4BD1T-Power-Torque-Curves
8
CarCrafter22, thread entry: 67 Ford F100 with Isuzu 4BD1T, 4BT Swaps, 10 Feb 2009.
http://www.4btswaps.com/forum/showthread.php?3300-67-Ford-F100-with-Isuzu-4BD1T
9
jdinevens, thread entry: d60s under a 4bd1t/2t, 4BT Swaps, 1 May 2012.
http://www.4btswaps.com/forum/showthread.php?23084-d60s-under-a-4bd1t-2t
Cummins 4BTs aren’t uncommon engines, and there is a wealth of information about them on the forums. The
Cummins brand has minor deity status among diesel enthusiasts, so one should expect to pay a premium for these
engines. If one decides to go with a 4BT, then the best deals seem to be found when buying them complete with
the donor vehicle. Many that have been separated from the vehicle seem to be more expensive. Though I like the
Cummins brand, I didn’t limit myself to the 4BT when making my selection. Isuzu 4BD1Ts will typically be less
expensive than Cummins 4BTs.
When I found my 4BD1T, I was able to get a functioning (but grungy) engine. The yard I bought it from ran the
engine for me. As a mechanically-injected engine, it only required fuel lines and a pair of jumper wires connected
to the starter to get it running. They started it up, and I noticed some smoke when the throttle was blipped, but it
seemed to be running fairly smoothly. We didn’t run it for long, as they hadn’t connected coolant lines. They
showed me an inventory ticket for the engine, showing that the donor vehicle had 122,000 miles on it. It also
revealed that the engine had been sitting in their pole barn for about five years. They wanted $2,000 for the
engine, but I told them (honestly) that I couldn’t be sure it didn’t need an overhaul, and talked them down to
$1,500; which I paid on-the-spot in cash. I don’t think I could have found many other good diesel engines in this
price range; at least not locally. A smart bargain shopper can easily find a better deal on one of these engines, but
I’m certain a Cummins in similar condition would have cost at least twice as much. I was lucky enough to find out
that this engine needed no more than a good cleanup and renewed seals to work very well in my swap.
WHAT I’D DO DIFFEREN TLY
When I bought the engine, it was strapped to a pallet, making it easy to haul it home on a small trailer behind my
Cherokee. It was easy to transport and I didn’t have to pull it out of the donor vehicle. Storing and disposing of
the donor vehicle may have been a pain, too. I don’t have a homeowner’s association, but my neighbors may have
been distressed about seeing a partially-disassembled truck parked outside my barn for months at a time. It would
have been nice to have more parts from the donor, though. If I did this again, I would try to get my hands on the
solenoid pack used for cold starts and shutdown. It would also be nice to have the glow plug control box. I was
able to work around these missing items quite easily, but having them might make an installation more “civilized”
than mine. If I had found a cleaner engine, I would have spent less time scraping mud and grunge.
As I began the long process of cleaning up the engine, I started to look for the vehicle that it would power. I will
discuss that process in the next chapter.
CHAPTER THREE: VEHICLE SELECTION
In general, most people who enjoy working on cars are familiar with how to find and purchase a vehicle that is in
good condition. Very little changes when selecting a vehicle for an engine conversion. Unless you are prepared for
a very expensive or lengthy frame-off restoration, a rust-free vehicle with a solid drivetrain is desirable. In some
cases, one may find a good deal on a vehicle with an engine or transmission issue. Beware, though! If the engine
and/or transmission have been neglected, other issues may be lurking.
Because my vehicle would be a family hauler, I considered the ideal of a mid- or full-sized four-door pickup. With a
cap installed over the bed, these would offer ample cargo space for dogs and gear, while the human portion of the
family would sit in the climate-controlled cabin. I was looking for an inexpensive vehicle in the spring of 2011, and
I quickly found out that 4-door pickups were not available for a good price. Examining other options, I realized that
a large SUV would also work for my purposes, and found out that GMT-400 Suburbans from the late 90s were
surprisingly affordable. Some of the Suburbans I found online included pictures of the original window tags,
showing MSRP figures that made me wince. I simply can’t imagine paying $30,000 or more for any vehicle. The
original owners paid a steep price for these machines. Thankfully, they were fairly well built, and many were still in
good condition after more than a decade on the road. Excellent examples were available for 1/6th of the original
price or less. Since my purchase, I’ve seen nice-looking machines for even less. With rising gasoline prices, these
vehicles were being dumped in favor of more efficient transportation. With this in mind, it reeks of contradiction
to buy one of these for a fuel economy project, but that’s exactly what I did!
I found my 1999 Chevrolet K1500 Suburban about 100 miles from home. I saw the photos of this sharp-looking
machine online and ran the VIN through an online decoder, revealing that it was exactly what I was looking for. I
can’t find the very complete, free VIN decoder that I used almost two years ago, but it is worth paying a $15 fee to
pull up to 50 complete reports from http://www.compnine.com before driving long distances to look at vehicles.
CompNine provides very detailed reports on how a vehicle was equipped from the factory. These reports aren’t
meant to cover vehicle histories, like some other well-known services. CompNine’s reports include the axle gear
ratios, which are crucial for diesel fuel economy. If you are looking at a GM vehicle that is nearby, it is relatively
easy to look at regular production option (RPO) codes from the sticker in the glove box that provide an extensive
record of how a vehicle was equipped. RPO decoders can be found in a number of places on the internet, but
when you are looking primarily at axle gear ratios, http://www.sierragear.com/gm-rpo-axle-ratio-identificationcodes-3/ is a good source to consult. It correctly correlates the GU6 code from my sticker with a 3.42 axle gear
ratio.
I called to ensure that the Suburban was still available. Then, my wife, kids, and I went to look at it and took it for a
test drive. The body was rust-free with only a couple minor dings. The cloth interior looked like it was new; it
hardly showed any wear. After driving it, I knew that it needed some suspension work and an alignment, but
everything was functional. We talked the seller down to $5,700 and closed the deal on the spot. As we were
starting the paperwork, another prospective buyer showed up after driving a great distance to look at it. Boy was
she upset! We were glad we didn’t wait to take advantage of this deal.
The following discussion is about why this vehicle was ideal for my project. Anybody considering a similar
conversion to get a large but efficient vehicle may wish to follow a similar recipe. Others are likely to differ on the
choices they would make, but I will list the trades I examined throughout this book. In places, the details will be
sparing, but this book is primarily about what and why, rather than an exhaustive treatment of how this effort was
accomplished. My hope is to share the choices I made in a way that is helpful to others.
The Suburban offers three rows of seating plus cargo space behind the third row. The bench in the third row can
be folded and removed, providing a larger cargo space. The second row can be folded flat, making a space large
enough to haul 4’x8’ sheets of plywood with the barn doors closed. Recently my wife and I picked up some carpet
on a 12’ long roll. We thought we’d have to haul it with one of the doors open in back, but by running it between
the front seats and putting one end up on top of the dash, we were able to haul it in comfort with the doors
closed.
The Suburban’s size is excellent for hauling people and things. There is also some inherent safety with any vehicle
of this size and weight – especially when it’s sitting on a conventional frame, rather than unibody construction.
The size and weight, when combined with four wheel drive, are also helpful for traction in bad weather and the
ability to pull other vehicles out of the ditch (for this specific build, traction is also assisted by a limited slip rear
differential). That additional weight also means that the vehicle doesn’t get whipped around when pulling a trailer
down the highway. These aspects of the Suburban have made them popular family machines for several decades.
For the purposes of this conversion, there were a number of additional good features that I was aware of:
1.
2.
3.
4.
5.
6.
Like most full-sized trucks, it features a large engine compartment – making the installation of a diesel
engine a lot less painful. Also, the room between the frame rails allowed options for how the
transmission and transfer case could be positioned.
The GMT400 models are brick-shaped, macho-looking vehicles, rather than the curvy, more feminine
shapes that followed. GM’s market researchers must have realized that soccer moms are the primary
drivers of these vehicles, and worked to make them more appealing in that market.
Because the GMT400s were built for more than a decade, many of these vehicles are still on the road.
This creates a demand for parts and accessories, so parts are inexpensive and the aftermarket is welldeveloped.
The K1500 I purchased was equipped with 3.42 gears, keeping the rpms down at highway speeds. With
slightly upgraded tires and the overdrive transmission I used, the 4BD1T is only revving at 1900 rpm when
traveling at 70 mph. This is the ideal rpm for this engine; where it produces the most torque and its
highest efficiency. I had already performed a trade study on gear ratios, and had the results handy when I
decoded the VIN. When I saw that it had the 3.42 gears, it was worth the 100 mile drive to look at it. The
K2500 Suburbans are the same size, but come with heavier-duty suspension and brake systems
underneath. These would be positive attributes, but they typically come with 3.73 and 4.10 gear ratios –
making them rev too high for good diesel fuel economy.
Kits were available to mate the 4BD1T with the Chevy automatic transmissions (I didn’t know about the
NV4500 option until later).
This vehicle came with a 40 gallon fuel tank. This meant that with an efficient engine it would have an
incredible driving range.
WHAT I’D DO DIFFEREN TLY
I’ve never been a fan of GM – especially after the federal government bailed them out and became part-owners.
In my mind, the company became known as Government Motors. Government control of the means of production
is not a good sign in a country that is supposed to be free. The “too big to fail” attitude creates favored classes of
businesses and is one symptom of government and corporate collusion. The most accurate term for this is fascism.
It is also known as corporatism, crony capitalism, or even crapitalism. I think the term fascism is more direct and
doesn’t indirectly slander capitalism by using or modifying the word. This type of behavior destroys free markets
and is actually the opposite of capitalism.
Though I’m not happy with GM, I’m pretty happy with the choice I made. I went out into the market place and
found what I was looking for. I found a bargain on a cavernous vehicle with four wheel drive that could easily
accommodate the 4BD1T and looked very nice. Even though I used one of their vehicles for my project, I can still
stick it to GM by asking a simple question: Why couldn’t they build a vehicle as efficient as mine?
CHAPTER FOUR: TRANSMISSION
An important step in my diesel conversion project was to determine what transmission I would use. There were a
surprising number of options to choose from, and those will be discussed in this chapter. I will also discuss how
the transmission was easily modified for my application.
My Suburban is a K1500, with the “K” meaning that it is four wheel drive, and the “1500” putting it into the half
ton class. From what I’ve read, the body and frame are no different from the K2500 (3/4 ton) version of the
Suburban. The K2500, however, gets a beefier drivetrain, axles, springs, and brakes. Because I bought a K1500, I
wound up with a fairly weak 4L60E transmission and an NP 246 Auto-Trac transfer case. I will discuss transfer case
modifications in chapter five. After fishing around 4BTswaps.com for information, I found that some people had
used the 4L60E behind the 3.9 liter diesels, but they had issues with durability. So, I knew I would have to upgrade
to a stronger transmission.
MY FIRST CHOICE: 4L80E
The obvious upgrade would be to get the beefier 4L80E and install it. I found one on Craigslist for a mere $250 and
brought it home. I pulled the pan and cleaned things up. It looked like it was in good shape inside. Then I started
listing the other components I needed to make it work, and found myself questioning whether this approach
would yield the best results or value.
The 4L80E is an electronically-controlled transmission. Its positives include that adjustments can be made to shift
points and firmness without the messy, iterative process of dropping the pan and filter to fiddle with the valve
body. The negative side is that the 4L80E couldn’t simply use the Suburban’s ECU (electronic control unit) to
control it — at least not without some sophisticated programming changes with expensive equipment I don’t own.
Even then, I would need to fake inputs for a number of factors that a factory-type ECU would be looking for; ones
that wouldn’t normally be found on a mechanically-injected diesel engine. This approach could very quickly spiral
out of control in costs, without any guarantee of success. I didn’t want the process of programming the
transmission to become its own long-term engineering project.
So, I started looking for alternative approaches to controlling the transmission. A number of options are available
on the performance and hot rod market. These exist because many customizers and performance enthusiasts
choose to mate non-computerized, carbureted V-8s with a variety of performance upgrades to these
electronically-controlled transmissions (including high-lift cams, turbos, superchargers, nitrous oxide, high-stall
torque convertors, etc.). Even when these engines have the sensors that OEM ECUs expect to read, they are likely
to be confused by a setup that doesn’t resemble an OEM engine. The result could easily be a transmission that
isn’t engaging reliably or shifting at the right time; which isn’t likely to hold up in a high performance application.
Stand-alone electronic transmission controllers solve this problem. These connect to the transmission using a
harness with a connector to read the transmission’s internal state and send commands to internal valves.
Externally, these systems typically require engine rpm and throttle position information to function properly. In
this case, diesel enthusiasts benefit from the fact that there’s already a market created by the performance
enthusiasts. Multiple manufacturers build these systems, and they all compete on price, reliability, ease-ofinstallation, and the method used to program them.
When I was looking at transmission controllers, there were several options.
TCI (Torque Converters, Inc.) builds a device called the EZ-TCU. Model TCI-302820 would work with the 4L80E. It
features a handheld electronic interface used for tuning, including a pretty neat “dash” interface that allows the
tuner to see the state of several systems simultaneously. It allows for multiple modes to be set for different
driving styles and conditions. This system will even allow full-manual operation using paddle shifters.10 It was
$615 through Summit Racing at the time, and would require my older 4L80E to be upgraded to the internal
harness used in the 1993 or later years. Like all of the controllers I researched, it would require a throttle position
sensor. I was concerned about the flexibility of this system for meeting diesel needs – which include shifts and
converter lockups at much lower rpms than gasoline engines typically require. I would have been more confident
this system would do the job if it could be plugged into a laptop for more control over shift points, firmness, and
converter lockup.
Baumann (now US Shift.com) built a controller called the Optishift (with the latest version called the Quick 1).11 I
liked that this system had a handheld controller in addition to an ability to tune it using a laptop – meaning that it
would probably offer more flexibility for diesel tuning. This device has been used by a number of people on
10
TCI EZ-TCU™ Transmission Control Unit Instructions, 2010, pp 3.
http://news.compperformance.com/Instructions/CPG5-103.pdf
11
US shift.com Important News. http://www.usshift.com/ (accessed December 2013)
4BTswaps.com. Several have been impressed with the ease of tuning and how well it works. This device was $550
at the time, with another $125 for the harness.
Powertrain Control Solutions (PCS) builds a controller called the Simpleshift. This system doesn’t have any fancy
displays, but uses a series of knobs to adjust shift points, firmness, and converter lockup. Because the shift points
are set up the same for all gears, I had some concerns about the flexibility of this system for my needs. At the
time, the device was $600. They are still selling the model I researched, the TCM-2300, but the MSRP has dropped
to $550. The harness adapter would cost an additional $25.
As you may have noticed, the controller costs were fairly similar, thanks to free-market competition. So my choice
would be based on features and how flexible the systems would be for use behind a low-revving diesel engine. I
was heavily considering the Baumann device, thinking that it was the most flexible. To make it work, I needed the
items in the table below. Like any good engineer, I built a spreadsheet to help me quantify my choices, price out
“what if” scenarios, and make an informed decision. The table below provides some of that information, and will
be explained in the following paragraphs, as I explore what a decision to use the Baumann Optishift controller
would have cost.
Price list for electronically-controlled transmission components
Item
Cost
Notes
Transmission
$250
Sourced locally from Craigslist
Baumann Optishift
$550
Most flexible controller, happy customer reports
Harness & Connector
$125
Adapts Optishift to transmission
Solenoid
$50
Optishift recommended upgrading
Remote Throttle Position Sensor
$50
Assuming I make my own bracket
Low Stall Converter
$300
Lower stall required than for gasoline engines
Rear Differential Upgrade
$400
Issues reported by others required an upgrade
Adapter Kit
$700
Adapter kit
First, the transmission would require an upgrade to the internal solenoid to work with the Optishift. I believe a
later year transmission would have come with the right one in it, but I got such a deal for $250 that I thought I
would still come out ahead.
The remote throttle position sensor would essentially be a spring-loaded potentiometer (variable resistor) to let
the controller know the throttle position. Knowing engine load allows the controller to determine the right shift
point for current conditions. Higher load (throttle) conditions will hold the transmission in a lower gear until
higher rpms are reached to maximize available power. Transitions from lower to higher load conditions will also
result in downshifts. Low load conditions will result in earlier shifts and holding higher gears for better economy.
To get the throttle input, I would fabricate a bracket and run a cable from my throttle to a remotely-mounted
sensor. $50 only included the sensor itself – so parts for the bracket and the cable weren’t included.
When I put this price list together I had already ordered a low stall converter. It’s important to remember that this
engine produces its peak torque and efficiency at around 1900 rpm. Ideally, the transmission/converter
combination should allow full converter lockup to make maximum use of the engine’s capabilities at this rpm (and
lower, if possible). I did some research on commercially available vehicles with diesels with automatic
transmissions. I found out that this condition wasn’t met in many applications. This is because the automatic
transmissions used are typically designed for gasoline engines and retrofitted for use behind diesels. This is
suboptimal, because these transmissions aren’t fully engaged until after these engines rev past the point where
they deliver their maximum torque. Better transmission designs would allow these machines to deliver more
torque to the drive tires and achieve higher levels of efficiency.
Though automatic transmissions are often used successfully in diesel conversions, I read about situations where
the transmissions were damaged or had behaved erratically under normal driving conditions. In my discussions
with Rod Brace, who had dropped an Isuzu diesel into a Suburban, I found out that he had experienced a hard 1-2
shift while idling around in a parking lot. The results removed all of the teeth from his differential’s ring gear. This
meant that using the 4L80E would require a heavier-duty differential than the one in my K1500. I estimated that I
could put an improved, heavy-duty ring gear and pinion into my existing differential for around $400. This added
another cost to my list, and there was still no guarantee that this system would stand up to the loads that it might
experience.
I continued my research and wound up talking with Diesel Tim (Tim Brotzge) from 4BDConversions.com. He
explained that automatic transmissions designed for gasoline engines often have problems in diesel conversions,
because their pumps haven’t reached proper operating pressures at rpms where we would like them to fully
engage or shift gears. This provided an excellent explanation for Rod’s unexpectedly hard, gear-stripping upshift. I
was preparing to research pump modifications to obtain higher pressures at low rpms, but I never got around to it.
I also knew that I’d need to swap the transmission’s tailshaft and housing to make the Craigslist two-wheel drive
tranny mate with my transfer case. My cost estimate was rapidly escalating. Any transmission I used would need
an adapter to connect with the 4BD1T, so I subtracted that $700 cost from my list, and found myself considering
$1700+ required to use a cheap Craigslist transmission. I was still assuming that this transmission was perfectly
functional and didn’t require a complete rebuild. So, cost and risk were both increasing by the minute. There
were many opportunities for failure with high impacts on project timing and budget. So, I widened the set of
choices that I would consider and wound up taking another path entirely.
THE BEST CHOICE: NV4500 5-SPEED
From my discussion with Diesel Tim, I decided that the NV4500 5-speed manual transmission was a better choice.
These transmissions are known for being bulletproof and are popular with off-roaders. This option would remove
a great deal of complexity from the drivetrain— giving me a system that would maximize durability while sticking
to readily-available components. I found that I could get an NV4500 from a GM pickup that would fit in the
Suburban and bolt to my transfer case. The GMT400 Suburbans share much of the running gear and components
used on the pickups of that body style. A quick look at the Suburban’s firewall and floor revealed what I already
suspected: areas designed to be cut out for the clutch master cylinder and for a manual shift lever. I also found
one of the two studs used to mount the clutch assembly under the dash.
An important contribution to this decision was Tim’s approach to the adapter kit. The kit from
4BDConversions.com uses an interesting combination of off-the-shelf components along with his custommachined adapter plate to create a robust solution. Though they come from a few different manufacturers and
are designed for different applications, each component is used as it was designed to be used. NV4500
transmissions aren’t cheap, but I realized that this option would offer the following benefits:



No electronic or electrical headaches. My brain would be the only necessary computer in the drivetrain,
and it’s already been programmed to control a manual transmission. With a mechanically-injected
4BD1T, the only wires required to drive the machine would be the ones connected to the starter.
As previously mentioned, only minor adaptations would be required, because NV4500 transmissions are
an option in GMT400 trucks.
The NV4500 features a 0.73 overdrive (5th gear) ratio. When combined with a 3.42 axle ratio and
265/75R16 tires, the vehicle would cruise at 70 mph with the engine revving at 1900 rpm – where the
4BD1T produces its peak torque and fuel economy. (If you’d like the calculation spreadsheet I used, email
me at [email protected].)


No rear differential upgrade would be required, as there wouldn’t be any unexpected hard shifts creating
excessive loads.
The NV4500 should be bulletproof behind a small 3.9 liter turbodiesel, as this 5-speed is also used behind
many 5.9 liter Cummins engines in Dodge applications.
There’s another feature of the NV4500 that some independent-minded people will like. My friends pointed out
that the combination of a manual transmission and a mechanically-injected diesel engine would result in a
drivetrain that’s immune to electromagnetic pulse (EMP) or high power microwave (HPM) attacks. I covered these
phenomena in chapter one, and the use of a manual transmission contributes to a drivetrain with no electronics
required for operation.
I used some online salvage yard search tools to find my NV4500, as the salvage yards in Indianapolis and the
surrounding area were picked clean. Standard transmissions are rare in modern vehicles, and the NV4500 is in
high demand for off-roading. I bought it from a salvage yard online, and it was delivered to me for a total of
$1,200. It shipped with a guarantee for the price of what a local rebuild would cost, so I thought this was a good
deal. I found it outside my garage on a pallet when I came home from work about a week later. The adapter
components (including a machined Isuzu manual bellhousing) cost me another $850. When the costs are added
up, they are very similar to using the automatic transmission, but I knew that this would be the most durable setup
with the lowest risk of failure. There’s also something to be said for the novelty of a GMT400 Suburban with a
standard transmission!
TRANSMISSION MODIFICATIONS
Although the NV4500 transmission was used in GMT400 trucks and would get along with my Suburban’s body and
chassis, it still required some modifications and adaptations to mate with an Isuzu 4BD1T.
Because it came from a Chevy 4×4, the bolt pattern on the rear of the transmission would allow it to bolt to the
stock NP246 transfer case, except that the NV4500 had 32 splines, while the NP246 transfer case had 27 (matching
the 4L60E). I had to swap transfer case input shafts, a subject covered in chapter five.
The 4BDConversions.com adapter requires the use of the longer, beefier 1 ¼” diameter, 10-spline input shaft and
housing that was found on Dodge versions of the transmission. I found these on eBay, and my local parts stores
had the needed bearings and seals. The correct seal part numbers were found by looking up parts for a 1994-2005
Dodge 2500 with the Cummins turbo diesel engine and a 5-speed manual transmission.
During this process, I had some difficulties pressing the bearing onto the new input shaft. So, I made a run to my
local Rural King (one of my favorite stores!) and visited their plumbing section. They are used to seeing me walking
in with random diesel parts, looking for something that I can improvise or adapt to work. It is true that a number
of tractor parts have made their way into this Suburban.
I found a piece of pipe and a coupler that happened to be almost the right diameter to push the bearing in place. I
used a bench grinder to put a taper on the coupler, ensuring that it would only contact the inner bearing race and
not the bearing carrier. I didn’t have a hydraulic press, yet, so I set this on a piece of plywood and hammered on
the pipe until the bearing was properly seated. Similarly, I used a block of wood to seat a new race in the bearing
retainer. I had to use the corner of a 2×4 to get this to seat below the retainer’s surface, but this was not a supertight fit and the approach worked fine. I also installed an oil seal in the retainer using a cheap Harbor Freight seal
driver.
I used a drill-mounted wire brush to clean up the mating surfaces. I stuffed some rags inside the transmission to
keep rust and metal filings from finding their way into the case. I packed synthetic assembly grease into the
bearing and coated the gear surfaces, too. I was ready to install the shaft and retainer, but I needed to use the
retainer to align the adapter plate first.
The 4BDConversions kit consists of a billet adapter plate, a Dodge clutch, and a pilot bushing. Because I purchased
my engine by itself on a pallet, I didn’t have a bellhousing. Because the engine had been bolted to an automatic
transmission, the bellhousing would have been the wrong one anyway. So, I wound up paying a bit extra for an
Isuzu standard transmission bellhousing. Tim Brotzge’s machinist modified the bellhousing by adding four blind
holes to clear the transmission input housing’s bolt heads. These can be seen in the photograph as four spots of
bright aluminum just inside the adapter plate’s large hole. I believe that the shaft hole in the bellhousing was also
machined to match the input shaft housing’s outer diameter.
The unpacking photograph shows the components as they arrived, except that I had temporarily attached the
adapter plate using the included flush Allen-headed bolts.
I cleaned up the aluminum bellhousing and sprayed it with some blue engine paint to protect it from corrosion.
Then, as described on the 4BDConversions.com website, I dropped the snout of the transmission’s input shaft
housing into the hole in the bellhousing. With this in place, I placed the adapter plate onto the bellhousing –
ensuring that the countersunk side of the six attachment holes were pointed upwards. This allowed the Allen bolts
to be installed flush with the plate’s surface. There was no doubt how things should align and the parts went
together smoothly. I torqued the bolts down and slipped the input shaft housing back out of the assembly.
The input shaft and housing were installed into the front of the NV4500. I used some RTV silicone sealant on the
mating surfaces to avoid leaks.
I bolted the bellhousing to the transmission. The transmission had been covered in surface rust, so I cleaned it up
and painted it to match the now-pretty bellhousing. This was a good moment to stand back and admire this Chevy
transmission with a Dodge input shaft and an Isuzu bellhousing. Everything went together in a slick manner, and
one could be led to believe that these parts belonged together.
The transmission discussion, however, is not complete, without covering the clutch, throwout bearing, and
fork. The Isuzu bell housing has a place to bolt a clutch slave cylinder externally and a pair of ears which would be
on the vehicle’s lower right side (visible in the last photo on the lower left). Of course, the slave cylinder actuates a
fork to disengage the clutch. Per Tim’s instructions, I picked up a throwout bearing for a Dodge pickup equipped
with a Cummins turbodiesel and a variant of this transmission. The fork is a stock Isuzu NPR component ordered
from NPRparts.com. It pays to have a VIN handy for these orders, and I found one online for a 1989 NPR truck with
a manual transmission. If you buy an engine on a pallet with only minimal information on the truck it came from
(as I did), look for trucks of the appropriate model and correct year for sale online. These ads often include VINs so
that prospective buyers can check vehicle records. The Dodge throwout bearing rides on the input shaft retainer’s
long snout, with the ability to slide forward and aft. The Isuzu fork required only a small amount of material to be
removed between the tines to fit around the throwout bearing — requiring only a few minutes of touch-up with a
cutting wheel on my rotary tool. As Tim mentions on his site, I ensured that the spring clips on the throwout
bearing were properly engaged with the throwout bearing, and snapped the fork’s retention feature onto a
supporting ball-joint built into the bellhousing. I also ordered and installed an Isuzu boot that creates a seal where
the fork exits the hole in the side of the bellhousing.
WHAT I’D DO DIFFEREN TLY
I don’t think I’d change the decisions I made in this part of the project. I have no worries with this transmission
setup and everything is sound. I’ve heard it said that “The best way to fix an automatic tranny is to replace it with
a manual one.” I feel much more comfortable with this than I would with an automatic transmission in this
application. With the tall gearing of a 3.42 axle ratio, I reached my target of 1900 rpm at 70 mph, but sometimes
the distance between gears seems large. If a bulletproof 6-speed transmission were available for a similar price, I
might consider it. There was a 6-speed NV5600 that was put in the Dodge pickups, but the production runs were
short (meaning that parts would be expensive) and the bellhousings were integral – making a kit like
4BDConversions.com’s more difficult to create.
I have nothing but praise for the kit from 4BDConversions.com, as everything went together very smoothly. The
kit wasn’t cheap, but when the bellhousing option is added to the kit the package cost is comparable to
competitor’s adapter kits for the 4BD engines or what Advance Adapters would charge for a similar package
(noting, of course, that Advance sells no adapters for Isuzu 4BD engines). Note, also, that conversions for 4BD
engines are certainly niche products, and it’s tough to make a profit on short production runs.
Tim Brotzge is working with Rod Brace, prototyping adapters for automatic transmissions as I write this. By the
time this is published, 4BDConversions.com may have some new adapters available. They are building adapters
for Dodge transmissions first, followed by Chevrolet. Ford and Toyota adapters may also follow, if there’s enough
interest.
CHAPTER FIVE: TRANSFER CASE
My K1500 Suburban came with an electronically controlled NP246 Autotrac transfer case. While some would push
for an upgrade to a manually-operated, beefier transfer case with rock-crawler gears, I was on a budget. This
Suburban was to be a family hauler with four wheel drive, not a rock crawler or serious off-roader. There are some
complaints about this transfer case’s durability. It seems that many issues stem from an oil pump design flaw that
eventually wears through the case, causing the fluid to leak out. This is a well-known problem, and I’ll address how
it was prevented later in this chapter.
Another issue, I believe, stems from the use of the automatic four-wheel-drive feature. This transfer case has
speed sensors on the front and rear output shafts. In the automatic mode, the truck operates in 2 wheel drive,
while a circuit looks for differences between front and rear shaft speeds. If wheelspin begins in two wheel drive,
the shaft to the rear wheels suddenly begins to spin faster than the shaft to the front wheels. When this is
observed, this system engages a pack of clutches internal to the transfer case, engaging the front shaft. Because
slippage has already begun, these clutches will slip a bit until the front and rear shafts are synchronized again. I
believe that this mode is a nice convenience, but I also believe that this type of operation is likely to wear out the
clutches if it is used often on slippery surfaces. Also, when it engages it may be a somewhat sudden event, so I’d
be concerned about whether the vehicle behaves predictably under those conditions. If things are slippery enough
to warrant the use of four wheel drive, it would be better to simply engage four wheel drive, rather than using
such a system as a crutch. I had no intent to use this mode, so I’m not too concerned about how it affects the
durability of the system. I also believe that some problems are caused by owners who replace their tires in sets of
two. Even though the numbers stamped on the sidewalls of tires stating their width, aspect ratio, and rim size may
be identical, the overall diameters of the tires will vary from one line of tires to the next. When used in automatic
mode, the system will see differences between front and rear shaft speeds, but it won’t know that this condition is
caused by different tire diameters. The result causes continuous clutch engagement and wear. I believe that by
avoiding the use of the automatic 4x4 mode, the life of this transfer case can be extended. Further, if this transfer
case ever gave me any problems, I could upgrade later.
To operate correctly, this transfer case required the support of some electronics in the vehicle. I believe that if this
system were disabled by an EMP or a high power microwave attack, the servos that engage clutches and select
high/low ranges would simply stay in their current positions. If the vehicle is in two wheel drive, it would stay that
way. The same goes for four wheel drive. Again, I’m not that concerned about these types of attacks, but I believe
the vehicle would still be drivable after one.
Because I would use the stock transfer case, I decided to leave it in its stock position; which dictated where the
transmission and engine would sit. This allowed me to avoid length modifications to the front and rear drive
shafts. So, the transfer case part sounds easy, right? I still had one issue that I had to address.
The automatic transmission that came with the Suburban was a 4L60E with a 27 spline (male) output shaft. The
transfer case’s female 27 spline input shaft wasn’t going to mate with the NV4500’s 32 spline output shaft. I did
some research, finding people who had converted GMT400s from this era to manual transmissions. They tended
to have manually-operated transfer cases, but they were of the same New Process brand, and had parts in
common. I knew there was hope for making this work, and I hunted around the Web looking for part numbers.
When I came upon drivetrain.com, I found the answer I was looking for. The useful exploded view on the
Drivetrain.com website showed two different input shafts, though it mistakenly identified them as having 27 and
32 teeth rather than splines. Their parts list for the parts got it right, though. I found out that the 27 spline shaft
was part number TRS-352670B, while the 32 spline shaft I needed was part number TRS-391670. 12
On that same page at drivetrain.com I found details on the pump wear problem experienced with this type of
transfer case. Simply stated, even though the pump is made of soft aluminum, the NP246’s magnesium case is
even softer. The pump has an edge that will eventually cut through a corner in the case’s wall. So, they sell a
drop-in piece of stamped sheet metal that reinforces the wear point, preventing the leak. I did buy some
components from drivetrain.com, including their Transfer Case Repair Saver. I purchased a 32-spline input shaft in
good condition from eBay.
TRANSFER CASE DISASSEMBLY
Unfortunately, there isn’t a simple cover that can be removed from the front of the transfer case to replace one
input shaft with another. The transfer case had to be split open, and most of its innards had to be removed to
access this part. I took extensive photos of the process and carefully laid the components out on the workbench
surface so that I’d remember how to reassemble everything properly. It sounds like a scary job, but it wasn’t really
that bad. It was time consuming, however.
Because the case is magnesium, it is surprisingly light. I picked it up, put it on my workbench, and started taking it
apart. I had some issues getting the case halves to separate, until I pulled a rubber plug in the tail housing and
opened the retaining clip behind it. When I had it apart, I was impressed with how clean it was inside. I didn't see
much wear for a vehicle with 151,000 miles on it. I figured that the vehicle had been well-maintained.
12
Drivetrain.com Transfer Case NP246 Rebuild Kits, Parts and Drawing.
http://www.drivetrain.com/parts_catalog/transfer_case_replacements_and_parts/np246.html (accessed
December 2013)
I carefully removed the chain, the main shaft, the clutch pack, and noted where all the parts came from. Then I saw
the fork inside--blocking access to the planetary gear assembly.
I had to buy a very large Allen wrench to remove the bolts that hold the fork from the outside of the case. My local
stores didn't have any this size (12mm), so I ordered it online. When the tool arrived, I was able to remove the
planetary gears and extract the input shaft from their center.
After replacing the front seal, I got out the synthetic assembly grease and started to reverse the process. When I
got to the point where I was ready to reinstall the rear case, I reached into my supplies and pulled out the case
saver I had purchased. The location where the pump wears on the case is in one of the pockets around the shaft.
The case saver is the steel ring shown here that sits in those pockets and provides wear protection to the
magnesium case.
Looking at these pockets, I saw very little wear on the magnesium. I expected to see more evidence of this
vehicle’s 151,000 miles. With the long life offered by a robust diesel engine, I hope to put several hundred
thousand more miles on this transfer case. This part cost around $40, which seems excessive for a piece of sheet
metal that was cut and stamped to shape, but it's cheap insurance for the long-run.
When reassembling, I found it best to set the case saver directly on the pump, as it would fall out of the rear case
when maneuvering it into position. When reassembling, be sure not to forget the lock ring that holds the chain
sprocket on the forward output shaft (seen in the upper-left corner of case saver installation photo). I wondered
what was going to hold that sprocket in position for a bit, before I located the lock ring and realized where it
belonged. Be very methodical about disassembly and reassembly. If you get confused, consult some exploded
views of the transfer case online.
When I had reassembled the transfer case, I was able to bolt it to the NV4500 and trial-fit it into the Suburban.
Because there was no hole for the shifter, I purposely left the transmission’s shift tower removed. I located where
I'd need to cut a hole in the tunnel for the shifter—which was close to the stamped area that was designed to be
cut out. Fortunately, I found out that transmission’s bell housing put the engine in a nearly ideal location. The
engine, transmission, and transfer case wound up mounted in a position 1.5" to the right, but the driveline angles
didn't change significantly.
WHAT I’D DO DIFFEREN TLY
There’s very little I would change about my approach with the transfer case. Having all the right fluids, parts, and
seals handy is a key to getting this type of job done quickly. Doing it quickly is important, so that you don’t forget
which parts came from what location. I only lacked an exceptionally large Allen wrench used to remove the bolts
that form the clutch fork’s pivot. The heads for the two Allen bolts holding the fork are actually outside of the
case, so it should be easy to measure them and check their size before cracking open the case.
Since this vehicle has been on the road, I’ve had multiple opportunities to engage four wheel drive in winter
driving conditions. Four wheel high is functioning flawlessly and engages quickly on the fly. I haven’t been able to
engage four wheel low, however. If I decide to fix this, I’ll need to look at the circuit diagrams on AllDataDIY or
Mitchell1. I will probably have to jump a circuit to convince the four wheel drive controller that the vehicle is in
neutral. It’s probably as simple as grounding or applying 12 volts to a pin on the controller. Because I’m not into
off-roading, I’ve never found four wheel low to be that useful, and the NV4500 has a pretty low first gear. Fixing
four wheel low is such a low priority that I may never get around to it. For grins, I also tried the automatic feature
in some deep snow on a gravel road in the Rockies—but it wasn’t working and I’m not sure why. It may be looking
for a missing ECU input, but I have no intention to fix it.
CHAPTER SIX: ENGINE PREPARATION
Though I had seen my newly-procured 4BD1T run at the salvage yard, what I brought home was a largely unknown
item. I knew it started easily and ran, but I wasn’t sure what I would find when I dug into it. Even if this engine had
been a known, perfect specimen of Japanese diesel engineering, I would still have a lot to do to make it work in my
application. Frankly, I had no idea how many details would have to be considered to make it work.
One of the most valuable resources you will ever find for the 4BD1T is Dougal’s thread on 4BTswaps.com called
STICKY: Isuzu 4BD1T/4BD2T Reference.13 That thread continues to be maintained by Dougal, and contains loads of
information, including links to the factory manuals for several Isuzu diesel engines, and a few discoveries I made
along the way. I cannot say enough about how helpful it is to have access to the 4BD1T manual. It answered many
of my questions, providing maintenance procedures along with clearance and torque specifications.
CLEANING THE ENGINE
As the engine was brought out into broad daylight and loaded onto my trailer, I noticed that every single part of
the engine had been painted black. As I started to dig in, I found that there was a lot of grunge and mud on the
engine under that black coating.
13
Dougal Hiscock thread STICKY: Isuzu 4BD1T/4BD2T Reference, 4BT Swaps, 25 Mar 2008.
http://www.4btswaps.com/forum/showthread.php?3635-STICKY-Isuzu-4BD1T-4BD2T-Reference
I dropped by Harbor Freight to pick up a pressure washing wand. While I was there I picked up a heavy duty
engine stand and a few other things I needed. The pressure washer connects to an air compressor and has a hose
with a weighted end that can be dropped into a container of water, degreaser, or the solvent of your choice. I
used this with some degreaser and a number of implements (including screwdrivers and wire brushes) to remove
much of the gunk from this engine. The effort that goes into de-gunking one of these engines shouldn’t be
underestimated! Removing accessories definitely helps in accessing the engine surfaces. Many of the accessories
wouldn’t be used in this application, so they needed to come off anyway.
When the engine was cleaned up, I sprayed it with some engine paint in a cast color, with some components
highlighted in semi-gloss black or blue paint. Wherever I could, aluminum parts were simply cleaned off and
“polished” with a wire brush on a cordless drill. Note that I accomplished many simultaneous tasks on this effort,
and (for purposes of readability) the organization of this book is not necessarily sequential. A sharp eye will quickly
reveal that the photos shown in this book are not actually shown in the sequence that they were taken.
CHECKING THE ENGINE
De-gunking the engine would be an ongoing process for several weeks, but while I was doing this I started
disassembling things to take a look at the engine’s internals. When I removed the valve cover from the engine, I
was pleasantly surprised and much less worried about the internal condition of this engine. The valve train was
clean, with no sludge whatsoever.
I picked up a diesel compression tester at Harbor Freight and performed a cold compression test. I made sure the
shut off lever on the injection pump was pulled and wired into the “shut down” position, as I didn’t want the
engine starting up on the stand and hopping around on my barn’s floor. When I simply connected jumper cables
and a switch to the starter, I found out just how current-intensive starting this engine would be. I could only turn
the engine slowly. I wound up buying some 2 gauge welding cable, ring terminals, and battery connectors. After
assembling these cables and making some solid electrical connections, I was able to turn the engine over with no
problems using an 800 CCA Optima battery. From the Isuzu manual, I found the compression spec to be 313 to
441 psi. Even though the engine was cold, I got a consistent 380 psi on all four cylinders. This engine was looking
to be quite healthy, and I was very happy with my purchase.
I rotated the engine to one side on the stand, so that I could access the oil pan and remove it. Again, I was very
happy with what I saw. In addition to the beefiest crankshaft I’ve ever laid eyes on, everything inside was clean
and sludge-free. Turning the crank and looking up into the cylinder bores, I saw smooth, shiny liners. I pulled the
main bearing caps one at a time, applying Plastigage to check clearances. I torqued the huge main bolts to their
175 ft-lb spec (I had to order a huge torque wrench for this!), then pulled them back off and used the scale on the
Plastigage packaging to determine what the actual clearances were. They were all within tolerance, so I cleaned
the Plastigage from the bearings, reassembled everything, and opted not to go through the connecting rods. After
my inspections and the compression check, I felt satisfied that the engine was healthy and wouldn’t need an
overhaul.
INJECTORS
I saw a bit of smoke from the engine when it was run at the salvage yard. I also read some advice that it was good
to clean injectors on any diesel engine that has been sitting for a while. So, I pulled the injectors and had them
cleaned at a local diesel injection shop. Clean injectors with a good spray pattern are important for the efficient
function of any direct-injection diesel engine. The shop told me that three out of the four were leaky and all had
bad spray patterns. I sent them to Rod Brace who knew a shop where the injectors could be rebuilt for less than
the $500 that my local shop was asking. I got them back a while later with a bill for $340, which wasn’t bad. I
installed them, using fresh seals from a full set of 4BD gaskets I found on eBay for $140. This was a good deal,
considering how much buying the gaskets separately would have cost – even though there were quite a few that I
didn’t use.
SEAL REPLACEMENT
I worked my way around the engine, replacing seals using the ones from the eBay kit, which seemed to work fine.
The most important seals were the ones for the valve cover, oil pan, front and rear mains, and the ones related to
the timing covers on the front of the engine. I was thoroughly impressed when I saw that the cam, timing pump,
and even the power steering pump are actually gear-driven. While the timing cover was removed, I rotated the
engine and checked to see that the timing mark alignments matched the ones in the Isuzu maintenance manual. I
didn’t touch the tappet cover seals, as they didn’t appear to be leaking. When dealing with an engine that is over
20 years old, the rubber gaskets will certainly be dry-rotted and in need of replacement.
INVERTING THE STARTER
I knew that there would be some challenges fitting the engine into my Suburban and maintaining four wheel drive.
One tip I’d received was to invert the starter, which hangs low on the engine’s left side and is likely to interfere
with objects such as the front differential. I never found any photos on how to do it. So, I posted my own photos
on the 4BTswaps.com site when I did it. The starter has a circular cup around its output shaft that fits into the
bellhousing on the 4BD1T. This maintains proper output shaft position relative to the engine’s flywheel. Many of
the starters I’ve seen over time have a bearing at the outer end of the output shaft, supported by an extension of
the housing with a cutout to expose the gear. This starter doesn’t have such a shroud, and the output shaft
extends from the starter in a cantilevered fashion, allowing the starter to be rotated to any angle that is
convenient. Stock geometry dictates that the starter clocks to a specific angle using three ears that must align with
the bellhousing’s studs. I measured the distances between these ears, finding that two ears were 120° apart, while
the third is purposely offset. Rotating the starter housing counter-clockwise (when seen from the front) one ear
will result in two ears engaging studs, while the third misses a stud and causes interference with the engine case. I
marked that ear, cut it off, and used a set of washers to hold the bottom of the starter in place using the starter’s
flange.
The only concern I had with the new starter position is that the positive terminal is close to and pointed directly at
the engine block. When I ran the 2 gauge cable to the starter after the engine was installed, I put a red boot over
the top of the ring terminal. Otherwise, ugly things could happen if a metallic object (such as a tool) is dropped
into the gap between the starter and engine block. 2 gauge cable can carry 1000 amps or more, so some arc
welding would likely take place and the short could result in an exploding battery. I would want to be far away if
something like that happened! Placing a boot over the positive terminal is some cheap insurance to avoid a
potential disaster.
PUMP TIMING
While the engine was still on the stand, I decided to check the pump timing. If necessary, adjustments would be
easier on the stand. The tag on the timing cover had said something about California emissions, so I expected that
some adjustments would be needed. To meet California emissions, the injection events on these engines were
retarded – much like the central planners themselves. While reducing emissions, this hurts engine efficiency and
reduces its output. I’ve seen dampers slip on other engines, so I try not to rely on their markings. I found the
crank’s top dead center position by shining a light into the #1 glow plug hole, watching the piston rise and fall as I
rotated the crank. I found out that the mark on the damper had slipped significantly, and I was a little concerned
that it might continue slipping over time and be less effective at damping out engine vibrations. I checked around
online, found a new damper on eBay for $100, and bought it. A nice benefit of using this damper was that it had
three V-belt slots in it, instead of the stock damper’s two. This would enhance my choices when hanging beltdriven accessories on the engine.
When I installed the new damper, I checked the timing mark and found that it was dead-on. Now I could check the
injection timing. With the engine at top dead center I removed the timing cap on the front of the injection pump.
I confirmed that the timing mark was aligned with the pointer. I ran lines from a plastic measuring cup filled with
diesel fuel to the injection pump, primed it, and disconnected the line from the pump’s #1 exit port. I made sure
that the shutoff lever wasn’t in the “off” position, as fuel needed to flow for this operation. I connected a breaker
bar to the bolt on the front of the crankshaft and slowly turned the engine over while watching the fluid level in
the port. When the injection event happened, the fluid level suddenly rose. I was able to confirm that this
engine’s timing was retarded. My measurements showed that timing was set at 7-8 degrees before top dead
center, while the manual shows a specification of 13 degrees. I state a range for my measurement, because it’s
hard to watch the fluid rise in the port while simultaneously watching the timing markings. I took repeated
measurements in order to ensure repeatability and accuracy.
Next, I marked the original location of the pump with a punch. Then, I loosened the four bolts that connect it to
the block. Accessing the upper left bolt is very difficult, but I was able to use a series of extensions and a universal
joint on my socket to back it off. At this point, the pump was adjustable by rotating it relative to the block.
Because the timing gear on the front of the pump turns clockwise when viewed from the front, the same direction
as the crankshaft, timing is advanced by tilting the top of the pump away from the engine block (counterclockwise,
as seen from the front). I believe that there are some erroneous posts on this point in some of the forums, so
think it through carefully. Some of the confusion may come from the 4BTs, which mount the injection pump on
the other side of the engine. The photo of the timing gears included in the seal replacement section should help
one to visualize which way the pump should be rotated to advance or retard the timing. Because the injection
lines acted like springs and wanted to return the pump to its original position, I used a tool to gently pry the top of
the pump away from the block and hold it in place. Then I tightened the two easily accessible bolts and found
where the injection event occurred again. I repeated this until I reached 13-14 degrees before top dead center.
Then I torqued down all four bolts and marked the new location with a punch.
PRE-INSTALLATION SENSORS
To be functional, the 4BD1T to be installed in my Suburban would only require electrical connections to the starter
motor. However, no gear head will be comfortable dropping an engine into their vehicle without the means to
properly monitor it. My Suburban had gauges for oil pressure, coolant temperature, and a tachometer in the dash.
Not only did I want the information, it would just be wrong to have gauges in the dash that weren’t operational.
Further, this turbodiesel would be tuned and modified over time, so adequate monitoring would be necessary.
It is important to note that as I removed the 5.7 liter V8 from the Suburban I didn’t slice any wires. I carefully
disconnected the connections, marking them with masking tape and a marker. When I couldn’t identify a
connector’s purpose, I went to Rock Auto’s site, looked up a 1999 Suburban, and typed “connector” in the search
box. Their site is not only a great place to find good prices on parts, it actually makes it easy to know which
connectors are which without all the back-and-forth that would be done on most other auto parts sites. The
layout of their site provided thumbnail pictures of many parts simultaneously. I do not recommend cutting off
connectors until you are sure that you won’t need that part of the wiring harness. Cutting off unnecessary
connectors should be one of the last steps in a conversion such as this one.
OIL PRESSURE
Whenever possible, it’s always best to use the sensors from the vehicle’s original engine to take the same
measurements on the “new” engine. This provides some assurance that the sensors will be properly calibrated
and the gauges in the dash will provide good readings. On the 4BD1T, the oil pressure sensor is on the engine’s
right side, just in front of the flywheel and above the oil filter adaptor. It bolts directly into the side of the block. I
removed it with the intention of installing the oil pressure sensor from the V8. The threads appeared to be 1/8
NPT, but I couldn’t get an adapter that size to fit into the hole. After some more research, I wound up buying Auto
Meter part number 2269, which is 1/8 British Standard Pipe Thread on the male end and 1/8 NPT on the other.
The oil pressure sensor is ¼ NPT and quite long, so I used a 1/4 NPT right angle adapter, a 1/4 to 1/8 NPT adapter,
and the Auto Meter adapter. This combination keeps the assembly close to the block – avoiding potential
interference issues with other components.
COOLANT TEMPERATURE
The area around the thermostat on the 4BD1T had four different temperature sensors. I’m not certain what they
were all used for, but I only had a use for one of them. The only closed-loop system requiring a temperature input
was the controller for the radiator fans that will be covered in chapter nine. This system used a sensor on the
radiator. So, I only needed to send a signal to the gauge. For this, I simply pulled out one of the Isuzu sensors and
installed the appropriate Chevy sensor. It’s important to use the right one, though. The V8 had two temperature
sensors. One was used to feed signals to the electronic control unit (ECU), while the other sends a signal to the
gauge. Early on, I found that I was using the wrong one and the other was still installed in the V8, which had been
sold for some time. This wasn’t an expensive part and it was available at my local store. The sensor for driving the
gauge is the one that comes with a boot and wire pigtail leading to a connector – not the one with the connector
hard-mounted on the sensor.
ENGINE RPM
Tachometers on gasoline engines normally read a signal from the ignition coil indicating every ignition event.
Sophisticated, modern, common rail diesel engines have position sensors to precisely measure not only rev speed
but the actual position of the crank, because this knowledge is used to trigger the injectors at the right times
during the cycle. Non-electronic diesel engines have to resort to other means to measure revs, because there is no
coil to provide this signal.
The stock alternator on the 4BD1T was used to provide a tachometer signal for the NPR truck’s tachometer. The
Isuzu alternator isn’t used on my installation, because of my vehicle’s electrical power demands. When I upgraded
to the 140 amp GM alternator, I found out that I could get a tach output from it. This was an option, but there was
another that I preferred.
The 4BD1T has a Hall effect sensor installed that sends an electrical pulse every time a tooth on the injection pump
gear passes it. Seeing this sensor’s presence, I decided not to add any sensors to the crank or flywheel. This
sensor would send 25 signals for every revolution of the engine, while the V8 sent only four (four-stroke engines
ignite the mixture on alternating revolutions). I will cover how the signal was converted to provide correct
tachometer function in chapter nine.
EGT & BOOST GAUGES
For tuning a diesel engine for performance and efficiency, it is important to know not only engine rpm, but the
current boost pressure and exhaust gas temperatures (EGTs). Visual indication of EGTs is important, because a
diesel engine can be destroyed if temperatures increase beyond safe levels in the combustion chamber.
Measuring the exhaust gas temperature provides the best indication of this, and this knowledge can prevent
damage that would affect the valves and turbo first, followed by other engine components. Turbochargers are
used to keep these temperatures down by injecting more air into the system – allowing power to be increased
without hurting engine longevity. So, knowledge of boost is also important. Tuners will work to balance EGTs and
boost when maximizing efficiency. If the turbo is underperforming or a hose pops off, boost pressures will drop,
and the operator will know to reduce fueling to avoid damaging the engine while monitoring EGT increases to keep
them at safe levels.
A number of companies make EGT and Boost gauges. I chose the VDO gauges because they were inexpensive and
because the color scheme of white print on a black background with orange needles matches the stock instrument
cluster. I mounted them using an inexpensive A-pillar dual pod mount that I found on eBay. The installation of the
sensors was not complicated.
The EGT gauge included a K-type thermocouple to be installed in the exhaust system. Ideally, these are installed in
the exhaust manifold before the turbocharger’s turbine. As the exhaust gasses run through the turbine, energy is
extracted. The extraction of energy results in a drop in exhaust temperature and pressure. The thermocouple
should be installed as close to the engine as possible, and it should certainly be upstream of the turbocharger’s
turbine. In my original installation with the stock turbo, I didn’t see much room on the exhaust manifold, so I
drilled and tapped the entrance to the turbine housing. I placed a shop rag inside the turbine housing to keep
metal chips out of the turbine. Afterwards, I pulled out the shop rag and was careful to clean out all the metal
chips that remained the turbine housing, which would blow through the turbine and cause damage. It is important
not to do this with the turbo installed on the exhaust manifold, as it would be impossible to remove all of the
chips. This setup worked with no issues.
The boost gauge measures air pressure in the gauge itself, so a line is run to a tap on the intake manifold. The VDO
gauge came with a basic installation kit, but the hose wasn’t long enough to reach the intake manifold. In the
United States, the convention for longitudinally-mounted engines is to place the intake manifold on the left side of
the engine and the exhaust on the right side. This makes for shorter, more convenient throttle linkages in vehicles
where the driver sits on the left side. In Japan, the conventions are reversed, as drivers sit on the right side of the
vehicle. So, the intake on the 4BD1T is on the vehicle’s right side, and the line that came with the gauge wasn’t
long enough. I ordered a kit with a longer length of tubing online. I removed the tubing that ran from the turbo to
the intake manifold. I put a shop rag inside the intake manifold to keep aluminum chips from migrating deep into
the plenum or runners. Then, I drilled and tapped the intake manifold’s inlet flange to accept the line fitting.
Before reinstalling the plumbing from the turbo, I carefully removed the shop rag and any chips of aluminum that
remained inside the intake manifold. When the engine was installed, it wasn’t any great feat of engineering to run
the nylon line from this point to the Suburban’s A-pillar.
WHAT I’D DO DIFFEREN TLY
I think I generally made good decisions in this process, based on what I knew at the time. However, there’s no
need for the reader to learn things the hard way that I did.
If I ever buy another super-grungy engine like this one, again, I’ll certainly stop at a car wash somewhere and
power-wash as much gunk off the thing as I can. The Harbor Freight wand worked well, but I believe the
commercial power washers provide more pressure. Perhaps a higher quality wand would also have helped. Degrunging the engine was extremely time-consuming!
I will cover my turbo upgrade in chapter ten. I held off on upgrading the turbo, because I didn’t want to incur the
additional expense if it wasn’t necessary. After driving the vehicle, I felt that it was. If I had known for certain that
I would upgrade turbos right away, I would have purchased and installed the new turbo before installation. The
upgrade would have been easier outside the engine compartment and I would have avoided building two different
downpipes.
I should move the coolant temperature sensor to one of the positions below the thermostat, instead of on the
neck above it. Because the coolant isn’t really flowing when the thermostat is closed, I don’t get any temperature
reading at the gauge until the engine reaches normal operating temperature and the thermostat opens. It would
still let me know if things started overheating, but it’s also nice to see status as the engine warms up.
MOVING FORWARD
So far, I’ve provided detail on things that everybody thinks about when they decide to put an engine into another
vehicle. As these chapters are written, you will find that the subject matter will continue into many details that
somebody might not consider. We always think about the powertrain as a propulsion system for the vehicle—
which it certainly is. However, it’s easy to forget that it is also the heart of the vehicle, with many systems that
need to directly interface with it. Every system that interfaced with the engine needed to be modified, and some
were significant efforts. I will ensure that all of the major systems are covered in the chapters that follow.
CHAPTER SEVEN: ENGINE-MOUNTED ACCESSORIES
Other than presenting a grungy mess that needed to be cleaned, preparing the engine really wasn’t a terribly large
or difficult effort. I did, however, spend a surprising amount of time figuring out how to hang the engine-driven
accessories on the Isuzu 4BD1T.
The engine came with a stock air conditioning pump, alternator, fan, and shroud. I removed all of these
components and used none of them. The fan was large and mounted quite high on the engine. It would have
required extensive modifications to fit under the hood. I chose to install a pair of 16 inch electric fans on the
radiator, instead. These would theoretically reduce parasitic drag losses on the engine and help with fuel
economy. This also allowed for a cleaner installation overall.
I knew I would need three accessories for this Suburban to be a fully functional, safe, comfortable vehicle for
family trips: a power steering pump, an alternator, and an air conditioning compressor. The power steering was
simplified by the fact that the 4BD1T came with a gear-driven power steering pump installed. So, that left me
figuring out how to install the alternator and air conditioning compressor.
ALTERNATOR
The stock alternator on the 4BD1T plays three roles as used in the NPR trucks. First, of course, is that it generates
electrical power for the vehicle. It is small and a bit anemic in this department, as it only produces around 70
amps. It also provides a signal for the tachometer and has a vacuum pump mounted on its back side. I already had
other ideas on how to make the tachometer work, but I knew the vacuum pump would be useful.
The Suburban’s stock alternator was designed to deliver at least 100 amps. Because this vehicle has front and rear
air conditioning systems and a number of other electrical accessories that would produce a high electrical demand,
I figured that I should go with the larger alternator – though I would lose the Isuzu’s vacuum pump and would have
to supply another system for my brake booster.
The 4BD1T’s alternator was located down low on what would be the vehicle’s left side. On the Suburban, I quickly
realized that this location would put it in a space occupied by my steering box. The alternator would have to be
moved upwards to clear it, and so I started looking for creative ways to mount the alternator a bit higher. I looked
at one of the heavy-duty brackets that was used to mount the original air conditioning compressor. It had some
features I wanted, but it would push the alternator further from the block than I wanted. So, I made some
markings with a permanent marker and chopped off some unnecessary metal with a reciprocating saw. Though
my markings (see the photo) indicated two cuts at right angles, I wound up deciding to make only a single straight
cut. This gave me a through-hole parallel to the engine’s crank – perfect for mounting an adjustable bracket for
the alternator.
I built the upper bracket assembly from flat pieces of steel, threaded rod, nuts, washers, and pieces of black pipe.
The black pipe segments were used as spacers, putting the grooves in the dual V-belt pulley in-plane with the ones
on the damper. I found that the upper assembly pictured here gave the alternator too many degrees of freedom
for movement, so later I replaced the rear arm with one made from a larger piece of steel with a notch in it,
indexing it to my customized mount and locking it into a fixed position.
So far, the bracketry was only supporting the top of the alternator. So, the bottom of the alternator needed to be
connected. I wanted this to be adjustable, so I used two pieces of angle iron. One was bolted to a couple
conveniently-placed holes in the engine block, and the other was hinged on that one. The movable piece of angle
iron had a slot cut into it, allowing the belt to be tensioned.
I should mention that the Chevy alternator came with a serpentine pulley in it. I was able to mount the V-belt
pulley from the Isuzu alternator on it. I don’t recall if I had to use any washers for spacing, but I recall that it fit
without any hassle.
Later, when I got everything together and the Suburban was driveable, I was charging the air conditioning in my
driveway and I found an unexpected problem. During this process, I was running front and rear air conditioning
systems simultaneously at full blast. This turned on the dual 16 inch electric fans, which were pulling air across the
condensor. With the engine at idle speed the battery was being drained. The low voltage on the Suburban’s
gauge signaled the issue. When I shut the engine down, of course it wouldn’t start. I put a charger on the battery
and looked at what could be done to increase alternator capacity.
I realized that the Isuzu pulley was too large, reducing the alternator rpms. I also realized that the stock Suburban
didn’t have a pair of 16 inch electric fans or an electric vacuum pump (covered in chapter nine), each of which
would draw considerable amperage. The stock 105 amp, CS130 alternator wasn’t adequate for job – at least not at
idle with a large pulley installed. I estimated that if I had 100 amps at idle, the system could idle indefinitely with
all of these systems turned on.
As engineers have been known to do, I opened a spreadsheet and started entering equations. First, I knew the
engine was idling at about 800 rpm. With a 6.5 inch diameter pulley on the damper and a 3.25 inch diameter
pulley on the alternator, the alternator was turning at 1600 rpm. This didn’t sound terrible, but then I found some
tables showing output versus rpm for my alternator. Even with a 105 amp rating, the CS130 alternator would put
out only 35 amps at this speed. So, the battery was being discharged at tens of amps with everything turned on at
idle. Not good!
So, my spreadsheet started growing, as I examined options and started listing other alternators that were
available. I found a number of options that used GM CS144 cases that had been rewound for high current output
in emergency and law enforcement vehicle applications. These would bolt up with my brackets and could produce
200 amps or more, but they were incredibly expensive! I looked at the stock serpentine pulley, realized how large
the Isuzu pulley was, and started to search for a smaller one to increase alternator rpms. I didn’t expect to find
much, but I was surprised. I found a 2.6” pulley from Great Water Marine Systems (www.great-water.com, part
number AM-2521) that was perfect for the job. Upgrading to this pulley would increase alternator speed from
1600 to 2000 rpm at idle. With the existing GM CS130, this would increase output to a still-inadequate 50 amps –
but it was certainly a move in the right direction. I saw that I could get a reasonable deal on a remanufactured GM
CS144 from Napa Auto Parts. Looking up the current vs. rpm curves for this alternator, I saw that this 140 amp
alternator would produce around 95 amps at 2000 rpm. I judged that this was close enough to my 100 amp goal
and could be purchased for a fraction of the other high-current options. Sold! I upgraded to this alternator along
with the smaller Great Water pulley. Since the upgrade, I’ve never had another issue with adequate electrical
power in this vehicle.
AIR CONDITIONING
The 4BD1T came with a large air conditioning compressor hanging on its lower left side, even lower than the
alternator. I knew that this position wouldn’t work in my installation, and the plumbing on the 4BD1T’s air
conditioning compressor didn’t look like it would be easily matched with the Suburban’s systems. Rather than
reengineering the entire air conditioning system, I chose to see what I could do with existing components. This
way I would avoid headaches by sticking to components that were designed to work with each other. It would also
be easier to find replacement parts.
I had seen where others had machined custom pulleys to put serpentine belts on the Isuzu and Cummins diesel
engines, but I thought I’d stick with the V-belt system. I had already made that choice when I installed the
alternator. I looked at options to get a dual V-belt pulley on the front of the Delco compressor and didn’t find
anything. As I hunted around, I found that the Sanden compressors were known for good quality and were
adaptable to a number of different configurations. There was a number of options for the pulley on the front –
including a dual V-belt pulley. The Sanden SD7H15 compressor would be a direct drop-in replacement for the
Delco compressor I had, complete with the top-mount line connections that would connect with the Suburban’s
stock lines. Sanden also sells a line of different adaptors for different line connection options; which would be
convenient if I needed to do some creative plumbing later (which proved to be unnecessary). I purchased an
SD7H15, which came with a standard serpentine pulley. I found a CL 1036C dual-belt clutch/pulley assembly on
eBay. When swapping pulleys I had to adjust the clutch spacing with some thin washers, but this was a relatively
easy swap.
I had to figure out where I was going to put the compressor on the engine and where it would sit in the engine
compartment. The Chevy V-8 had a mount for the compressor on the top left (driver’s) side, while the
dryer/accumulator, evaporator, and condenser connections were all on the engine compartment’s right side.
Looking at what would be a fairly tall engine installation, especially with a stock tube from the turbocharger to the
intake that ran over the top of the engine, I thought I might have issues crossing over the top of the engine with
the stock lines. I looked into crimping equipment that would allow me to assemble custom lines or extend my
existing ones. After recovering from a severe case of sticker shock, I decided to stick with the stock lines, if at all
possible. I loosely connected the stock lines to the compressor and, with some estimated measurements for
engine position in-hand, started experimenting to determine where the compressor could be placed without
pinching or crimping the lines. I found that the compressor would sit nicely at the upper right side of the engine
without any issues. The lines would take some unusual paths, but they wouldn’t be terribly stressed.
Now that I had a good idea where the compressor would be, I had to figure out how I was going to mount it in that
position. After mulling over a number of options, I decided that I could remove four of the bolts surrounding the
fuel injection gear from the timing cover, replace them with threaded rod and nuts, and install a mounting plate in
this position. This would put a vertical plate in the plane of these mounting locations. Because the compressor
was designed to mount horizontally, and because I wanted to keep it level in terms of “clocking,” I looked for what
I could use as an adapter and found a solution in the pile of components I had removed from the engine. There
was an air conditioning mount that was a couple beefy pieces of 3/8” steel welded to make a T-shaped crosssection. This would bolt onto the plate I was making. I could drill fresh holes in it to place the compressor in the
right location. Much time was spent clamping components into place, measuring, and eyeballing locations before I
decided that this would work. I know that many engineers would spend a bunch of time creating 3D CAD models,
but I have a pretty good feel for these things and liked the idea of figuring things out as I went.
Now I had a pretty good idea what the shape of the mounting plate would be, so I picked up some 3/8” steel plate
to build it. I made a cardboard template and kept trimming until I thought it would fit. Then, I cut a plate to match
the template. I drilled the holes in the plate, one at a time, using a sharpened stud to locate the next hole each
time. Eventually, I had all four holes located and drilled. Then I loosely installed the plate and started fitting the
welded bracket. The new plate was somewhat triangular with a semi-circular cutout to fit around the injection
pump’s gear housing.
I drilled the first hole in the weldment and the new plate, putting a bolt through the two. Then, I used a clamp to
ensure the weldment’s top plate would be level and drilled the other hole. I measured the compressor position
that would place the two pulley grooves in-plane with the grooves at the front of the damper’s bolt-on pulley
extension (with the replacement damper and the extension, I had a total of five grooves available). I marked
where the compressor holes needed to be, made spacers from black pipe, drilled the holes, and bolted the
compressor to the platform with threaded rod and thread-locked nuts.
The compressor was in a fixed position, so I knew I would need a way to tension the long belts that would be in
this location. I had saved the tensioner from the Chevy V-8, and made some modifications to it. I put a pair of
pulleys from Rural King on it and mounted it to a plate cut from 3/8” steel that mounted on the front of the power
steering pump’s beefy housing. I had to play with the detent that would set the tension, but when I found the
right position I drilled it out and everything mounted up perfectly.
When the drivetrain was installed in the Suburban, I was very happy with the geometry I had chosen. It didn’t take
too many miles to find a problem caused by diesel vibration and the long, cantilevered tubes at the top of the
compressor. This is further upset by integral reservoirs built into those tubes. I don’t recall if the V-8 installation
had any supports for these, but I didn’t make any provisions for this, initially. So, on our first trip to Colorado after
the diesel conversion, one of the tubes broke and we went without air conditioning for the rest of the trip.
Thankfully, it was October and temperatures were dropping. We didn’t need the a/c again until spring. Over time,
the other tube broke as well, so I knew that replacement tubes would have to be properly supported.
In the spring, I replaced the lines with another stock set, but built brackets to support the lines at their integral
reservoirs. I used angle iron to create well-supported cradles, using large hose clamps and strips of EPDM to
provide cushioning. Thousands of miles later, the replacement lines are holding up without any signs of flexing or
cracking. While I was building these brackets, I also ran a piece of angle iron from one of the compressor mounting
studs to one of the intake manifold bolts—providing further support to keep the cantilevered bracket from
bouncing around. Diesel vibrations can be harsh, even with 3/8” steel plate for support. I had seen one of the four
studs holding the mounting bracket break over several months of use, and this seems to have fixed the problem.
WHAT I’D DO DIFFEREN TLY
In this chapter I’ve provided some detail on things that went wrong. It has been said that hindsight is always
20/20. If I did it over, I would certainly fix some of these problems before they ever surfaced. In summary, there
are two key points to watch for in this area:


Ensure that electrical modifications (e.g. dual radiator fans and an electric vacuum pump) are included
when figuring out what alternator to use. In a vehicle with equipment similar to my Suburban, I would
recommend going straight to a 140 amp alternator with a small pulley to increase the rpms.
Keep vibrations in mind and adequately support any components mounted on the engine. I’d especially
pay close attention to spindly aluminum pipes like the ones on the a/c compressor.
I may eventually add an additional idler pulley for the long belt on the a/c compressor. I’ve increased idle speed to
the 900 rpm range to smooth things out. When the a/c is engaged at 800 rpm or lower, the a/c belts find
resonance and bounce around. Adding a fixed idler pulley would stop this. There’s an unused boss on the water
pump that might be used to mount a pulley.
CHAPTER EIGHT: ENGINE AND TRANSMISSION I NSTALLATION
I won’t provide detail on removing the original engine, transmission, and transfer case, as I believe that any
gearhead or mechanically-inclined person can figure that out. Make certain to properly support things and use
good safety practices. You don’t want to get hurt or, worse yet, damage any hardware! During this process, I
believe it’s good practice to carefully label all of the connectors as they are unplugged. You will thank yourself
later. If there’s any doubt about a connector’s purpose while integrating the diesel engine, Rock Auto’s online
system is very useful for identification – but it’s much easier to label the connectors as you go.
As I began this part of the conversion process, most of the modifications to the engine, transmission, and transfer
case were complete. It was time to begin the actual installation. The fitting effort on a conversion like this
shouldn’t be underestimated. For me, this was a trial and error process with multiple iterations. The vehicle was
on jack stands and there wasn’t much extra space underneath the vehicle. I didn’t have a vehicle lift or a lot of
other specialized equipment, and I worked under conditions that would be common in a typical gearhead’s garage.
This iterative process involved:





Lifting and fitting heavy objects into position
Finding interferences and other integration issues
Removing the heavy objects
Making modifications
Repeating as necessary
On each iteration, the components moved closer to where they needed to be. I started by working out where the
transmission and transfer case would sit, and started fitting the engine later. It was a tedious process, but the
results were certainly worth the effort. In this chapter I provide some tips so that others don’t have to learn things
the hard way. It seems that I do everything in life the hard way, but I learn a lot that I can share.
FITTING THE TRANSMISSION AND MODIFYING T HE CROSSMEMBER
The transmission and transfer case were assembled on a piece of plywood and the assembly was slid underneath
the Suburban using plastic furniture sliders. It is worth noting that the NV4500 weighs roughly 200 lbs, even
without the NP246 attached. The assembly was jacked into position carefully using a pair of floor jacks and blocks
of wood. This was tricky, because the transfer case created asymmetric loads that had to be countered when
lifting the assembly. This was further complicated by the angles involved. In many instances the front of the
transmission was raised at an angle, in order to mate up with the engine.
I chose to avoid the fabrication of custom front and rear driveshafts, which would be required if the transfer case
were moved toward the front or the rear of the chassis. So, the transfer case remained in its stock fore/aft
position. The transmission mount on this vehicle is under the rear of the transmission, just forward of where it
connects to the transfer case. The transfer case bolts to the transmission where it hangs cantilevered. Because
the NV4500 was used in some GMT400 trucks, I expected to find a fair amount of interchangeability and was
proven right. I was able use the same mount that is used for the automatic transmissions in this vehicle, and it put
the transfer case in the correct location.
The transmission crossmember could have been left in place, but repeated fitting iterations meant that it would be
more convenient if it could be removed and reinstalled easily. The crossmember sits on top of the lower part of
the frame’s “C” cross section and is a tight fit. The torsion bars that act as springs for the front suspension pass
directly over the transmission crossmember, extending from a separate crossmember, positioned aft of the
transmission crossmember, to sockets in the lower control arms. These steel bars were in the way and had to be
removed. For more positional flexibility when mating the transmission and engine, it was good to have the torsion
rod crossmember out of the way, because the snout on the rear of the transfer case passes over the torsion bar
crossmember.
The torsion bars weren’t terribly difficult to remove, once I found the trick of using a bushing press to apply
pressure to the adjustable cams. The press was hooked over the top of the crossmember and tightened just
enough to back out the bolts and remove the adjusters. Then, I slowly, carefully backed off the bushing press,
relieving the potentially dangerous level of energy contained in these torsional springs. For safety’s sake, it is a
good idea to keep your body out from under the truck and away from these components during the operation.
With the tension released, I was able to push the bars forward into the lower control arms to disengage them from
the adjustment cams at their rear. When this is done, the cams will fall out of the crossmember onto the floor.
These cams are surprisingly heavy chunks of steel, and have a talent for falling on your head, if you aren’t careful.
Once they were released from the cams, I was able to pull the torsion bars aft, above their crossmember, and
remove them entirely. From some previous A-body Mopar experience, I knew that I could create a clamp from
some pieces of wood with semi-circular grooves and large bolts in them for a place to pound, if the bars were stuck
in place. Penetrating oil can be applied to both ends of the bars and left to sit overnight, if they are rusted into
place. I’ve used oil of wintergreen as a penetrant to loosen rusted components with great success. The stuff
smells great, but be sure to read up on the potential side effects of any chemicals you use. Pure oil of wintergreen
is actually quite toxic, and skin contact should be minimized. With the bars removed, I unbolted the torsion rod
crossmember and removed it, so that it would be out of the way.
With the torsion rods out of the way, I could maneuver the transmission crossmember out of its position between
the frame rails. After installing and removing the transmission and transfer case a few times, I realized that the
transmission might have to sit a little lower and that the process of maneuvering the crossmember in and out was
painful. I decided to move the crossmember below the frame. I’ve owned a few four-wheel-drive vehicles that
mount the crossmember this way, and figured that it should be possible. The main concern I had was that this
crossmember was fabricated from stamped pieces of sheetmetal that were welded together. The crossmember
structure clearly relies on being bolted firmly to the frame in order to be stiff enough not to fold. I was also
concerned that bolt heads might pull through metal if the crossmember is hanging from the frame, rather than on
top of it. So, I cut pieces of angle iron to appropriate lengths and drilled the needed holes into them. I used these
above the frame and below the crossmember as reinforcement. I also used a stack of washers as spacers to fill
gaps, adding further rigidity to the assembly. This made my further attempts at fitting the system much easier.
As I installed and removed the transmission and transfer case assembly multiple times, I was able to locate where
the shift tower needed to be and cut a hole in the floor. I used a sheet metal nibbler purchased from Harbor
Freight. Though I think I used up much of that tool’s useful life, it was less than $30 and I’d certainly buy one again
for this purpose. It made cutting sheet metal very easy. I purposely minimized the hole’s size until I had
determined exactly where the engine would sit and at what angle.
LIFTING THE ENGINE
I was using a heavy duty 2 ton cherry picker (shop crane) to lift the engine. To get the engine into position in the
Suburban’s engine bay with the vehicle on jack stands, the boom was extended to its maximum length. Due to the
physics of leverage, the boom markings indicated that the device’s capacity was limited to a mere ½ ton in this
position. A lighter-duty cherry picker would not have been adequate for lifting this 800 lb beast into place and
pulling it back out repeatedly. I had a load leveler / spreader bar, but I quickly found out that the engine would be
too close to the firewall for it to clear. I had to build my own low-profile spreader bar from pieces of square steel
tubing bolted together for stiffness. My custom device allowed me to get the engine balanced and into the right
position without any interference.
OIL FILTERS
As I was trial fitting the engine into the compartment, I found out that the engine’s stock oil filter setup wasn’t
going to work. The 4BD1T came with a pair of filters on a single adapter on its right side. It turned out that the
forward filter was going to run into the perch for the original engine mount on that side. Rod Brace had
mentioned this, but I thought my installation was different enough that I could make everything fit. It turned out
that I couldn’t do it with this oil filter adapter.
Several have actually machined their own adapters and remote-mounted filters on diesel conversions, but I wasn’t
ready to do that. Rod had mentioned that the later model 4BD2T used a single filter and that the assemblies were
interchangeable. I found one of these single filter assemblies on eBay and purchased it. It was very easy to change
to this adapter, as it bolted on with no modifications other than the use of a shorter bolt in one location. This
adapter uses a single coffee-can-sized filter that costs $40 a pop, but it sure helped the engine fit in the Suburban.
LOWERED FRONT DIFFERENTIAL
As the engine was inserted and removed from the engine compartment the first few times, I purposely left the oil
pan and sump uninstalled. I knew that they would interfere with the Suburban’s front axle. The 4BD1T is quite a
bit taller than the original V-8, so this an expected problem. I had to do a few things to ensure a good fit without
components banging into each other under load; potentially causing damage. I decided to lower the differential to
make more room.
Rod Brace had mentioned this as a good idea, and it led to thoughts about the geometry of this vehicle’s
independent front suspension. Because my Suburban spent more than a year on the jack stands in my barn, I
couldn’t remember the stock angle of the shafts or CV joints, so I paid close attention to GMT400 suspension
geometries I saw on the road and in parking lots. I noticed that at stock ride height the shafts on these vehicles left
the differential housing and went downward about two inches to get to the front wheel hubs. With a compressed
front suspension, it wouldn’t be unusual for these shafts to wind up level or even pointed slightly upwards. The
shafts would reach their minimum length when they reached their horizontal position. So, I knew that the shafts
wouldn’t be too long when used in a horizontal position. I had no intention to lift this vehicle, and I was interested
in lowering the front differential a couple inches. This would place the shafts in a nearly horizontal position at the
normal ride height. Rather than causing any harm, this geometry would actually put less stress on the CV joints
than the stock geometry. Also, at upper and lower maximum suspension travel, the angles would never be as
severe as they are with the differential in the stock position and the front wheels at full “droop.” So, I didn’t see
any issues with this geometry change.
It wouldn’t be terribly difficult to make brackets to move the front differential, but I really wanted to get this
project done as soon as possible. I chose to purchase the necessary components. Because GMT400 trucks are so
common, a number of companies build lift kits for them. Several lift kits lower the front differential to avoid
severe CV joint angles. Some of these kits use a bolt-on cradle that holds the differential in a lower position while
providing lower connection points for the control arms. Because I wasn’t after a suspension lift, these systems
wouldn’t work in my application. I found two companies using separate brackets to lower the differential. When I
called one of them, they told me that they wouldn’t sell me these parts for use without a lift kit. Obviously, they
weren’t good capitalists and didn’t want my business! Arguing with such a mentality is useless, so I called the
other company. Superlift is obviously run by proper capitalists who were very helpful. They sold me the parts to
lower the differential 2” for around $150. The parts I purchased were:




55-03-3250
55-04-3250
55-05-3250
55-06-3250
It would be good to find the part numbers for the bushings associated with these components, but I didn’t realize
that I needed them. I found some locally-available polyurethane bushings and trimmed them to fit. One might
also consider buying the bolts in the kit, but I buy grade 8.8 and 10.9 bolts at Rural King by the pound, and the
price is hard to beat.
On the differential’s left-rear side, I cut off an ear on the frame and bolted on the new 55-05-3250 bracket to
support it. On the front-left, I used a pair of extension ears, 55-03-3250 and 55-04-3250, to support the
differential in its new position. This is where I had to improvise a bushing, as previously mentioned. On the right
side, the support bar was replaced with part number 55-06-3250 that simply lowers the assembly.
This was a fairly straightforward modification that succeeded in making more room for the engine in the
Suburban’s engine compartment. As the Suburban sits at a stock ride height today, I can look at the shafts and see
that they are close to level, but they actually go upwards slightly as they pass from the differential assembly to the
wheel hubs on both sides.
Some may object to this modification because of the vehicle’s ground clearance. When I see GMT400 4x4 trucks
on the road, they show lots of ground clearance in the front because their front differentials are hidden behind the
chassis’ lower frame. After this modification, my front differential is visible when looking at the vehicle from the
front. I haven’t decreased the vehicle’s overall ground clearance, though, as it is no closer to the ground than the
rear differential.
ENGINE AND TRANSMISSION MOUNTS
As the transmission and transfer case positions were being sorted out, I started adding the engine to the equation.
As soon as I felt comfortable hanging the engine in the bay with the sump in place, I tried it out, so that I could take
measurements to figure out what oil pan modifications would be necessary. With the engine at the vehicle’s
centerline, held to the transmission’s bellhousing with a couple bolts, I learned a few things:



Flipping the starter was a great idea, as it would certainly have run into the lowered differential in its
stock location.
The coffee-can sized oil filter on the engine’s right side had plenty of space.
The sump was uncomfortably close to the differential on the left side – even after lowering the
differential.
I knew that this position wasn’t going to work. The sump position, where the oil pickup tube and screen are
located, wasn’t easily changed on this engine. This is the one feature below the engine’s bottom flange that
limited potential oil pan modifications. I judged that moving the engine an inch and a half to the right would fix my
problems.
For the purpose of keeping parallel driveline angles, I would move the transmission and transfer case to the right,
as well. The latter was actually quite simple. Over time, I discovered that I didn’t actually need to lower the
transmission as much as originally intended, so I had some room to move it back upwards. This allowed me to
insert a piece of 3/8 inch plate between the transmission mount and its perch on the crossmember. This shifted
the assembly to the right to match the engine’s relocation. I had to enlarge the shift tower hole in this direction,
as well, and did so without any issues. I was glad that I hadn’t made the hole in my floor any larger than it needed
to be.
I settled the engine into an approximation of its new location using pieces of 2x4s as temporary engine mounts.
Because the engine was being shifted to the right, I used two pieces of wood on the left side. The mount flanges
on the engine were just a bit too far forward to use the perches as they were. There was only a small overlap—
which can be seen in the photographs. The fact that there was an overlap meant that some good, stiff extensions
made to the perches wouldn’t be completely cantilevered.
I chose to use some common, off-the-shelf engine mounts for this installation. These are used in a number of
Chrysler Corporation (Mopar) applications, with studs on each side that are offset from each other. I chose some
with an additional safety feature that isn’t always found on these: interlocking wings that keep the mount from
separating too far if the rubber damper debonds itself from the metal endplates. The mount shown in the
photograph is one of the two I used. It was DEA Products part number A2469.
I built perch extensions from 3/8” steel plate, bolting each of them in place with four bolts attaching to the original
engine mount locations. I had to trim off ears that were inboard of the perches, and some allowances needed to
be cut out in the forward edges of the perches so that the engine mount studs could pass through and bolts could
be installed. Because the engine would come in vertically with the mounts installed, and the studs stick out at a 45
degree angle, slots needed to be cut in these plates rather than simple holes.
With the perches in place, and the mounts loosely bolted to the engine’s flanges, the engine was lowered into
position and bolted to the transmission. The mounts were rotated so that the studs would drop into the slots that
had been cut, and the engine rested on its mounts for the first time. In each photo, one of the plate-to-perch bolts
are missing. There was an interference issue with the upper-front bolts on each perch. This was corrected, and
currently all four perch extension bolts are in place on both sides.
When looking at the view of the right-side, the plate looks like it drooped, but the metal hasn’t been distorted in
any way. The flat surface on the perch was never parallel to the frame rail in this location. This setup has proven
to be very sturdy and I haven’t had any issues with it. Some might choose to use polyurethane mounts, but it
would be a poor choice with a diesel engine. I purposely chose rubber mounts to absorb as much vibration as
possible.
OIL PAN
Once the engine was sitting on its mounts, I took another look at the sump location. After I moved the engine to
the right I found that the sump had plenty of space. I took some measurements to ensure I would provide some
extra space around the differential without interfering with the sump. I made some cuts, removing a corner from
the lower part of the oil pan, and slipped it into place. I could see that this would work very well, so I hunted down
a welder on Craigslist. The welder did some quality work and I installed the pan. I’ve had no issues with leaks or
interference with the differential.
CLUTCH
When I was ready to start bolting the engine and transmission together in my fit checks, I needed to remove the
automatic flex plate and flywheel to avoid interference. This engine came from an NPR truck with an automatic
transmission. I had ordered a standard flywheel and pressure plate from a salvage yard online, and I needed to
install them. First, though, the automatic hardware needed to be removed. The flex plate was simply unbolted
from the flywheel, and the flywheel was easily removed with a puller.
The next step proved to be quite a headache. There was a pilot pressed into the back of the crankshaft that
needed to be removed. A different pilot would be used with the NV4500 and the Dodge clutch. This bushing was
a very tight press-fit and was very tough to remove. I started by checking out a blind hole puller set (OEM# 27128)
from Autozone as a loaner tool. This included a set of expanding heads in different sizes. The appropriately-sized
head would be inserted into the pilot’s hole, a nut would be tightened to expand its jaws, and a slide hammer
would be used to extract the pilot. It wasn’t that simple, though. When I used the slide hammer, I found that the
device would slide out rather than move the pilot.
I found some tips on the 4BTswaps site about filling the cavity with grease, then using a socket with a close-fitting
outer diameter and driving it in with a hammer. The resulting hydraulic pressure would push the pilot out. I
packed the cavity with grease and did all that I could to get air bubbles out. Then, I inserted the tightest fitting
socket I had on an extension and pounded away. It didn’t move. A variation of this was recommended by
nexxussian in the forums, where Lisle part number 55600 screws into the hole and a grease gun is connected to
the tool’s zerk fitting. The user pumps the grease gun, and the pressures build steadily until the pilot is pushed
out.14 I didn’t hear about this before my struggles, though, so I continued working to remove this thing using brute
force and junkyard mechanic ingenuity.
My best bet was to make the blind hole puller work, so I took some measurements. I found out that the puller
head wasn’t getting deep enough into the pilot to grab the shoulder at its far end. So, when I tightened the puller
head, it was trying to grab the smooth wall inside the pilot. I spent hours grinding a taper into the bushing’s inner
diameter. This allowed the puller’s head to be inserted deeply enough to reach the shoulder on the opposite side
of the bushing. I removed a lot of steel in this process, but I finally got the puller head far enough into the bushing
to engage properly. The slide hammer was still ineffective, though. Slow, steady pressure was needed for this job,
so I built a pulling tool from a section of 2” pipe with a cap on the end, some threaded rod, a nut, and a washer.
The threaded rod fit into the puller head, and tightening the nut outside the drilled cap pulled the bushing out. I
used a pipe wrench to keep the pipe from turning, and put a big wrench on the nut. Once I had the right tools in
place, it wasn’t a tough job.
14
Nexxussian thread entry: 4BD1T Into 1999 Suburban, 4BT Swaps, 16 Jan 2012.
http://www.4btswaps.com/forum/showthread.php?18880-4BD1T-Into-1999-Suburban/page2
While I was working in this area, I replaced the rear main seal, which was a very straightforward operation. I used
the one that came in a large kit of seals that I had purchased on eBay.
When I was ready to make a semi-permanent connection between the engine and the transmission, I installed the
manual flywheel, bushing, and clutch. The manual flywheel requires shorter bolts for installation than the
automatic flywheel did. I had to order them, and my notes show they were grade 9.8 M14 x 1.5 x 40mm bolts. The
Dodge/Cummins-compatible clutch was held in place and centered with the tool that was included in the 4BD
Conversions kit. Then the pressure plate was installed. Diesel Tim’s excellent instructions were followed, and can
be found here: http://www.4bdconversions.com/steps.htm
OTHER INSTALLATION DETAILS
The engine didn’t simply drop into place. It took a lengthy period of careful fitting and adjustments to make
everything fit. The engine went in and out of the engine compartment quite a few times, and it’s worth reminding
the reader of safety when dealing with such heavy objects on hydraulic lifting devices. Never expect a hydraulic
device, especially a used Harbor Freight cherry picker, to support anything for an extended period of time. Always
expect that these devices will settle slowly over time. My fitting sessions always ended with the engine sitting in
an improvised cradle on the floor made from plywood and blocks of lumber – at least until I had engine mounts or
other devices to safely support the load. This required thinking ahead and watching the clock during each session.
I had to reserve time to remove the engine before cleaning up for the day. Safety was also an important factor for
the Suburban itself, which sat on jack stands for quite a few months. Failure to follow smart practices can be
dangerous to fingers, hands, and even your life. Additionally, if items slip or settle it may cause damage to
expensive components.
Once I had the engine and transmission in what I was sure was the final position, I finished the process of cutting
the floor for the shifter. I used the holes in the bottom of the boot as a template, punching the spots where the
holes were going to be and using stainless, self-tapping screws to do the job. It’s important to note that it was
installed around an inch from the position that the knockouts and dimples in the stock sheetmetal would suggest –
so simply cutting the hole in the stock position would have been a bad choice. I made sure I didn’t use screws that
were too long, or they’d run into the top cover of the transmission below. I found a good deal on a Dodge shift
tower and shifter, but if I did it again I would have used Chevy components with a lower profile that wouldn’t
require adding a small bend to the shift lever. However, it’s all working quite well, and I’m satisfied.
WHAT I’D DO DIFFEREN TLY
Overall, I’m quite happy with how the most critical steps in the conversion process went. There was a lot of
potential for things to go wrong, but taking my time and being careful really paid off. As always, there are a
number of things I’d do differently, if I did it over. Several of these were covered in the text above, but a few more
items follow.
I never actually removed the condenser from the Suburban in this process. In hindsight, I think that mating the
transmission to the engine might have been a simpler process with the additional space this would have allowed. I
may have even decided to attach the engine, transmission, and transfer case as a single assembly and slid it into
the vehicle that way.
Everything seems to be working well, even though my approach minimized the need for welding. Only the oil pan
modifications and some turbo-related components (the latter discussed in chapter nine) required any welding. I
see a lot of value in what welding can do for the fabrication process, and I could have made a more robust set of
engine mounts with this capability. I’ve purchased a welder recently, and will certainly learn to make good quality
welds before performing another project like this.
Rod Brace gave me some tips recently about engine mounts. He has observed that these rubber mounts can go
out. He recommends drilling through them and running a bolt through from one plate to the other. He would put
a pair of locked nuts on the end, but wouldn’t tighten them down against the endplates. This way the mounts still
absorb vibration, but they provide some safety by acting in shear if the rubber portion of the mounts becomes
delaminated or cracked.
Writing this chapter reminded me of my exposed front differential. I’m not doing any off-roading, so the small loss
in clearance isn’t an issue for me. The front differential has an aluminum case, though, and is quite vulnerable to
road debris. After a chunk of steel in the road took out my Jetta TDI’s aluminum oil pan, I have been forcibly
reminded that road debris can cause very real issues. GM’s designers purposely tucked this differential behind a
steel cross-brace where road debris wasn’t likely to hit it. Many of the GMT400 trucks were also shipped with
additional skid plates to protect the front differential. I should really fabricate my own skid plate and install it
(probably a great project for somebody learning to weld).
With the engine and transmission in place, I was basically done with my project. Right? Wrong! Many other
systems required modification for this vehicle to be fully functional, and I will cover many of them in the next
chapter.
CHAPTER NINE: OTHER SYSTEMS
It’s easy to underestimate the magnitude of an effort like this one. Most will consider the adaptation and
mounting of the engine and transmission as the main portion of an engine swap, but there’s actually quite a bit
more to be done. Changing the engine from gasoline to diesel, changing the engine form factors (V-8 to inline
four), and changing from an automatic to a manual transmission affects many other systems, requiring
modifications for proper function.
CLUTCH HYDRAULICS
I discussed the installation of the clutch itself in Chapter Eight, in addition to cutting a hole in the floor for the
shifter. Other than repeated fitting and alignment checks, the conversion to a manual transmission wasn’t the
challenge that I expected it to be. Once it was in place, I still needed to make the clutch functional. Thankfully,
Chevies in these years used hydraulic clutches and the NPRs did, too. Running a flexible line from a Chevy master
cylinder to an Isuzu slave sounded like it wouldn’t be a tough challenge. If either of these vehicles used pushrods
or other mechanical linkages, this would have been much more difficult.
The Suburban shares a lot of sheet metal with other GMT400 vehicles, but GM likes to make changes over time,
even when exterior appearances remain the same. Some GMT400 clutch assemblies would fit this vehicle, and
some would not. I looked at the knockout for the master cylinder in the Suburban’s firewall, and sketched the
relative placement of the center hole and the two stud holes, so that I could find a matching clutch pedal assembly
at a salvage yard. On this vehicle, the left and right studs were level, relative to each other, and above the
centerline of the center hole.
I found the correct assembly at a salvage yard, cleaned it up, and put a fresh coat of black paint on it. These
assemblies have a pair of studs that go through the firewall and a square opening in the center that the master
cylinder locks into. On the horizontal portion of the bracket, there is a pair of holes for studs that would be found
under the dashboard. My Suburban had one of the two studs, and I intended to add the second stud later. I never
got around to it, as the three nuts and studs have been adequate to hold the assembly securely.
I drilled out the stud holes and also put a hole in the larger circular knockout large enough to insert my Harbor
Freight air nibbler. This device’s mandrel could only deal with limited sheet metal thickness, so it wouldn’t allow
the plunger to cut flush with the edges around the outside of the circle where another layer of sheet metal was
encountered. I removed what I could with that tool. I used a grinder on a rotary tool to remove the rest. As
shown in the photo, I trial-fitted the pedal bracket before grinding off the remaining metal in the hole. All of the
metal had to be removed for the master cylinder to be installed. I painted the metal in this area to avoid rust.
When this had dried, I applied some RTV to the inside of the large hole to keep moisture from getting into the cab,
installed the bracket, and bolted it down.
I purchased a new master cylinder at an auto parts store and had previously trial fitted it to the clutch pedal
bracket on my workbench. I was able to confirm that the included pushrod would interface properly with the
pedal. I also figured out how to attach the master cylinder to the bracket. So, I knew to rotate the master cylinder
to the vehicle’s left (my right), insert it, and turn it upright to lock it in place.
I found a local shop with a good reputation for making custom hydraulic lines. I took some measurements to
determine how long the line should be, and brought example parts along to show what the proper end fittings
should be. I showed them the slave cylinder connection that was on the far end of the stock Chevy line that was
attached to the NV4500 when I bought it. I also brought along the Isuzu slave cylinder that I would be using. I told
the fabricator I wanted a 90 degree bend on the slave cylinder end and a straight connection at the master cylinder
end. They built up a nice braided stainless line for me that worked beautifully.
To install it, I had to remove the master cylinder to access its underside and run the line down the firewall, where I
added a simple bracket to keep it from coming in contact with hot exhaust components (the exhaust is on the
vehicle’s left with the Isuzu engine, while a Cummins would have it on the right). I used some makeshift clamps
and piece of rubber hose where the line crosses beneath the engine to keep the braided steel from wearing on the
engine or vice versa. I installed the Isuzu slave cylinder on the bellhousing and connected the line. My son helped
top off the fluid in the master cylinder and bleed the system.
I was concerned about a mismatch in the volume displaced by the Chevy master cylinder and what the Isuzu slave
cylinder was expecting. At one extreme, the master may not have displaced enough fluid to disengage the clutch
at full pedal travel. I found out that the reverse is actually true, as the clutch pedal only needs to be depressed a
couple inches to disengage the clutch completely. At the other extreme, fully depressing the pedal could push the
slave cylinder piston entirely out of the bore at full pedal travel. This hasn’t been a problem, either. So, I got lucky
on this, and didn’t have to resort to limiting pedal travel or using a strange combination of components to make
this work.
FUEL SYSTEM
The fuel system required some modifications to deliver diesel fuel instead of gasoline.
First, I worked on the fuel tank. I syphoned out as much gasoline as I could and put it into cans for my mowers,
chainsaw, and other equipment. When the tank was removed, some gasoline was still found in the bottom. I
removed the cylinder containing the fuel pump and level sending unit. Then, I syphoned out the rest of the
gasoline that I could with the tank tilted toward one corner. Then I left it out in the sun to dry. When what was
remaining had fully evaporated, I wiped out any remaining crud with some rags. I left those out in the sun to dry,
also.
I removed the fuel pump from its cylinder, knowing that the viscosity of the diesel fuel would be wrong and that I
didn’t want 40+ psi of fuel pressure. I only needed a low-pressure pump so that the injection pump mounted on
the 4BD1T’s right side wouldn’t have to pull through long lines back to the tank. If there were any leaks, this would
result in air in the lines; causing the engine to run poorly or even damaging the pump. The low-pressure diesel
pump would be mounted externally, so I replaced the gasoline pump with a piece of stainless tubing. No other
changes were required here, so I reinstalled the cylinder. The fuel level measurement system would work with no
modifications required.
While the tank was out, I noticed that it was rusted pretty badly on the outside in some locations. There weren’t
any leaks, though, so I de-rusted, treated, and painted the tank before reinstalling it. The rubber anti-scuff pads
where the tank nests in the frame at the front and rear top edges had trapped water, making the “protected”
areas the rustiest. So, when I reinstalled them I squeezed a bunch of RTV into the gaps at their tops to keep
moisture out in the future.
Also, before reinstalling the tank, I looked at hose routing and made some modifications. The supply hose would
go from the tank to the low-pressure pump to the metal supply line running along the vehicle’s frame. The return
hose would function with no modifications required. The vent system hoses were removed and the connectors at
the top of the tank were blocked off – as diesel doesn’t evaporate the way that gasoline does, and this system was
unnecessary.
The fuel filler neck had to be modified. I checked online to see if I could simply purchase a diesel filler neck. They
were expensive enough that I chose to simply remove the unleaded-sized nozzle restrictor plate.
I used a green Mr. Gasket diesel pump, which I mounted on the frame right in front of the fuel tank. The electrical
connection for the in-tank pump was rerouted to the external fuel pump, while leaving the fuel level sending unit
connections in their stock condition. If I did this over, I might spend some time looking at the stock diesel lift
pumps, as I suspect these would drop right in and wouldn’t require as much modification.
The Suburban had a gasoline filter in the steel line running along the left frame rail near the middle of the vehicle’s
length. I removed this and filled the gap with a short length of diesel-compatible fuel hose. The low pressure
diesel pump has a coarse fuel filter mounted on it, and a fine filter hangs on the 4BD1T’s injection system.
EXHAUST
I would have kept the Suburban’s stock 2 3/4 inch exhaust, but it had a muffler with two inlets. As soon as I
started pricing ways to modify what I had, I realized that I could get an inexpensive three-inch exhaust system.
Diesel engines flow a high volume of exhaust gasses compared to gasoline engines – especially at mid-throttle
conditions. As a result, diesel engines respond very favorably to low-restriction exhausts. Improvements include
increases in power, torque and fuel economy. Because this was a fuel economy project, and because a 3.9 liter
engine isn’t exactly a huge engine for something as massive as a Suburban, a three inch diameter system would be
adequate. So, this decision turned into a no-brainer. The GMT400 Suburbans from 1994-1995 use a system with a
single inlet, so I chose to purchase an aftermarket system designed for those earlier years. I wound up with a
Flowmaster 17124 Force II system.
This cat-back system fit the later model Suburban very well. Some brackets had to be moved a bit, but that was
simply a matter of unbolting them and drilling holes in the new locations. Everything forward of this system would
have to be new, though. I chose to purchase 90⁰ and 45⁰ elbows, with lengths of steel exhaust tubing in a 3”
diameter to build the rest of the system myself. I used pipe expanders to create slip joints and a series of clamps
to hold it all together. I found a bargain price for a stack of 3” clamps on eBay. Later I found that some of the
included bolts would split, but those were cheap and easy to replace.
I tried a couple cheap pipe expanders from Harbor Freight and eBay. These wound up being poor choices. Finding
a good, reasonably-priced pipe expander for a non-professional mechanic is difficult. These first pipe expanders
were essentially a pair of cones held together by a threaded rod with a series of plates around the outside. The
plates had tapered surfaces riding on the cones. As the threaded rod was rotated, the cones were forced toward
each other, forcing the plates outwards. This, in theory, should provide excellent leverage for stretching the steel
tubing. I managed to make a single slip joint with the Harbor Freight tool, and the eBay-sourced item gave similar
results. In both cases, one of the cones split under load. These were a poor design made from cheap pot metal.
Apparently, $15-$25 is too cheap to do this job. These might have been adequate for rounding an oblong piece of
tubing, or for expanding some of the cheap, thin-walled exhaust parts found on the shelf in the auto parts stores.
For tubing with fairly stout 0.060” walls, however, they were not up to the job.
For attempt #3, I bought a name-brand Lisle 32750 pipe expander. I was doubling the cost in hopes of better
quality. Because the other design used a pair of cones with no restraint on the plates, there was nothing keeping
the expansions from becoming conical as the plates invariably favor sliding along one cone versus the other. The
Lisle 32750 solves that problem by using a pair of cones that work in the same direction against a cup on the end.
It also has anti-rotation features for the plates, which further help with the tool’s function. I managed to expand a
few pipes before I started stripping out the bolt that runs through the middle. I replaced the bolt a few times and
got a few more pipes expanded, but it wasn’t long before this device, too, made its way to the scrap pile.
Tool #4 was the Lisle 34400 with some add-ons allowing it to work on a range of pipe sizes up to 3”. This set cost
just over $100. This tool uses an automotive-type bearing on one end and a tapered nut with a square cross
section. A series of mandrels and extenders allows for expanding different pipe sizes. It would have saved time
and money to buy this tool first, but I have to learn everything the hard way! Even with this tool it’s hard to
expand 3” pipes with 0.060” walls. An air wrench helps get the job done. Every time I use this tool I pack fresh
grease into the bearing and coat all of the threads and sliding surfaces. Greasing the outside of the mandrels also
helps, by relieving friction that resists stretching the tubing.
If I did this over, I’d take a hard look at some of the less-expensive hydraulic systems for expanding pipes. They
cost several hundred dollars, but would have saved a lot of time.
The front of this exhaust system was later modified when I upgraded the turbo, but I only had to modify the
downpipe at the front end. Initially, I used the Isuzu downpipe, which was shortened and adapted to
accommodate the larger 3” pipes that followed. After that was a creative arrangement of elbows to get the
exhaust out of the engine compartment. In the pictures, you’ll note the many clamps used to hold everything
together. Now that I own a welder, any further modifications to this system will include some welds in these
areas. Even if welding is performed, clamping tubes is still a good first step for positioning tubes and elbows to
make everything fit. The clamps could be removed after the tubes are welded.
After the exhaust leaves the engine compartment, it needs to cross from the vehicle’s left to its right side. I found
out that passing under the transmission just behind the bell housing fit well, without hanging too low. After that,
the exhaust meets up with the Flowmaster system, which was sawed-off just in front of a bend where it crosses
over the torsion rod crossmember.
The Flowmaster system takes care of the rest. I should point out that the stock exhaust systems on these vehicles
exit quite low with a long horizontal piece, while the Flowmaster stays tucked away, exiting in a downward
direction. This arrangement is an improvement over stock, as it preserves more ground clearance. I’ve noticed
that the stock pipes on these vehicles often get banged up because they hang so low. It also directs potentially
sooty diesel exhaust at the ground, rather than at angles where it may be more noticeable or annoying to others.
INTAKE
I won’t spend much time talking about the first intake I built, because I completely reworked it when I upgraded
the turbo a few months later. I’m including it, though, in case others might wish to stick with the stock turbo or
use other turbos that will point their intakes toward the firewall. In this initial setup, I maintained the pipe that
passes over the engine from the turbo to the intake manifold. Getting clean air to the turbo was more difficult, as
the stock turbo inlet was pointed at my firewall. I used a sawed-off 90° 3” exhaust elbow with the stock seal for
this location. The seal was over 20 years old, but appeared to be polyurethane and the sealing surfaces were in
good condition. Because I made relief cuts in the end of the elbow, I was able to put a large stainless hose clamp
on it to make a secure connection.
Because the turbo sat pretty high and had its inlet pointing at the firewall, there wasn’t any room for the 90° elbow
to turn, except tucking between the engine and the firewall. Space was tight, but I didn’t see another option. I
finished the intake system using straight lengths of exhaust tubing, silicone elbows, and a cylindrical air filter. I
made a support from stainless sheet metal that bolted to the Suburban’s right fender – where the original air box
used to be.
COOLING SYSTEM
Diesel engines are inherently more efficient than gasoline engines. I’ve heard some claims that this was because of
engineering tolerances or other causes, but the real reason is that diesel engines use a thermodynamic cycle that is
more efficient than gasoline engines (Diesel cycle versus Otto cycle). Without going deep into thermodynamics,
the bottom line is that more of the energy stored in the fuel is turned into useable mechanical energy. For both
engine types the remaining balance of that energy is released as heat; meaning that gasoline engines produce
more heat. The result is that the gasoline engine radiator is actually oversized for my purposes, and I chose to use
the radiator I had.
I had already decided not to use the 4BD1T’s huge radiator fan. Others have used this fan, but cut down the blade
lengths to make it work. In my application, the water pump would sit above the radiator’s centerline and I really
didn’t want to create a custom shroud to make it work. I realized that I would be much better off with an electric
fan or two. Even when viscous fan clutches are functioning properly, some of the engine’s power is robbed to turn
the fan at all times. In theory, these clutches engage and the fans come up to full speed when the right
temperature is reached, but I’ve always been uncomfortable with this theory. I’m also unaware of a good way to
confirm that it is functioning properly. Electric fans do use engine power to operate, because all electric loads
result in loading up the alternator and electric system, but electric fans are only used when they are needed, and
are the right choice for a fuel economy project.
The Suburban’s radiator is just over sixteen inches tall and very wide. Initially, I chose to use a pair of inexpensive
electric fans I purchased on eBay. I mounted them as pullers, as the 1999 Suburban has a narrow space between
the radiator and grille. These fans were easily mounted using the included pieces of plastic that slide between the
radiator fins with ends that ratchet into place like zip ties. It’s important, also, to use the included rubber pads to
avoid damage to the fins and tubes in the radiator. Some have used plates to cover the areas between the fans,
but this keeps airflow generated by vehicle movement from flowing through those areas. I didn’t add a shroud or
cover to the radiator.
The cheap fans worked well for about a year, but they destroyed themselves on my last trip to Boulder, Colorado.
One of the fans threw some blades and ripped itself off its mounts – disconnecting the wires for both fans. I don’t
know when it happened, and I wasn’t aware of it until we were near the end of the trip. That part of the drive
involves a 2,000 foot climb in about 4 ½ miles, and I noticed the coolant temperatures reaching levels that I had
never seen before. Thankfully, I keep an infrared thermometer handy, and it showed that the engine
temperatures weren’t high enough to damage the anything, but I jumpered the remaining fan to stay on and cool
things down.
I wound up buying a pair of Imperial 226116 fans that are a much better design than the ones that I previously
used (the Hayden 3701 appears to be the same fan, and Imperial is a subdivision of Hayden). While the cheap
eBay fans had narrow, cantilevered blades that could easily break off, the Imperial fans have wider blades with
much beefier bases and a ring around the outside for further reinforcement. They look like they could be OEM
parts. These fans have a snap ring in the middle that can be popped off to reverse the blades for puller rather than
pusher operation (for behind the radiator rather than in front of it). I mounted these beefier fans in place of the
cheaper ones, and I haven’t had any issues with them.
The use of electric fans requires a signal to know when they are needed. Initially I used a Hayden 3647 controller.
That device failed after six months and I replaced it with a Flex-A-Lite 31149. Both devices use probes that slide
between the radiator fins to measure coolant temperature. These controllers can be adjusted to turn on at a
range of temperatures. Some other options came with preset activation temperatures, but I wanted additional
flexibility for my unusual application. The 4BD1T’s thermostat starts opening at 180°F and I wanted the fans to
come on at around 200°, I figured that the radiator should have a chance to do take care of heat rejection before
fans are turned on unnecessarily. This avoids unnecessary cycling of the relay and the fans. These systems, like
most of the others available, have an input for an additional trigger that was connected to the air conditioning
unit. When the air conditioning compressor’s clutch is engaged, the fans come on to cool the condenser.
To calibrate both of these controllers, I used an old 12 volt A/C adapter, some test leads, an LED light, a candy
thermometer, and a pot of water on my stove. I later replaced the candy thermometer with a meat thermometer,
because it had a faster reaction time. I connected the light to the fan output, so that I had a visual indication when
the circuit was activated. I dropped the probe into the water (keeping it off the bottom of the pot), and cycled the
heat while stirring the water, measuring temperatures, and adjusting the temperature adjustment knob until I had
it right. This is much better than calibrating temperatures by potentially overheating an expensive engine.
I had to connect the Isuzu engine to a Chevy radiator, and this took some creative engineering. I measured the
fittings that I needed to match and looked for suitable pieces of hose at a local automotive store. Thankfully, one
of the clerks was willing to let me come back behind the counter to look at what was available. I selected a
handful of hoses that I judged would work. I hacked them up and routed them where I needed them.
The hose from the engine’s thermostat to the top-left (vehicle’s left) of the radiator wasn’t too tough to work out.
I used a universal flex hose made by Dayco (#81201) that has a 1.5 inch inner diameter (ID) and is 25 inches long.
The ID was a little large for the radiator, so I used a piece of radiator hose that fit correctly as a bushing. I cut off a
piece that would fit over the radiator’s neck, slid it into place, and slipped the universal hose over that, using a
clamp to hold both in place. I had to tighten this once for a slow leak, but this joint hasn’t caused any further
problems.
The hose back from the lower right (vehicle’s right) of the radiator to the water pump took quite a bit more effort.
I had to use multiple pieces of hose and make it fit behind the air conditioning belts without rubbing on the air
conditioning compressor mount. I had built some clearance into the compressor mount to make room, but things
were still quite tight. In two places I found that I could make things fit if I could clamp one hose to another, as
one’s outer diameter (OD) matched the other’s ID very well. This sounds crazy, but when I realized I had some
steel tubing with an OD matching the smaller hose’s ID, I had a solution. By putting small sections of steel tubing
inside the smaller hoses, I now had something substantial that the outer hoses could clamp to. I maximized the
overlap between the two hoses at the joint. I used this method in two locations, and have had absolutely no issues
with either joint.
With this accomplished, I was able to route the hose where I wanted it to be. Over time, it pays to check hose
routings for any areas where the rubber is scuffing against metal – as nobody enjoys the sight of split hoses or
puddles of coolant on the ground.
The heater hoses were a trivial matter, as I simply needed to adapt sizes and run them in a manner that wouldn’t
kink them.
POWER STEERING
Hanging accessories on an engine that wasn’t designed for them can be a pain. Belt-driven accessories are also a
source of potential failure. I keep a container in the back of each of my vehicles containing useful supplies, such as
tools, spare bulbs, fuses, a first aid kit, a tow strap, jumper cables, etc. I also keep spare belts in these containers
for the same reason that vehicles have spare tires. They have been known to fail. Before I removed the engine
from the pallet it came on, I was identifying the components hanging on my newly-purchased 4BD1T. It was then
that I was overjoyed to find out that this engine came with a gear-driven power steering pump. This meant that I
had one less accessory to hang on the engine and fewer things to fail.
I still had to do some adaptations to make the power steering pump work with my stock Chevy steering box. My
cruddy old lines had been chopped up when I removed the V-8 from the Suburban. The remainders of the Isuzu
lines were crushed, and I didn’t have the reservoir that normally hangs on the engine. So, I was starting from
scratch for this system, except that I had the power steering pump and box as endpoints.
First, I figured out how to run the supply line. My local O’Reilly auto parts store had the stock power steering
pressure line assembly for my Suburban, and I thought that would make a good starting point – since it would at
least have the right connection at the steering box end. I believed that I would wind up paying somebody to
fabricate a custom line, but was glad to find that this was unnecessary. Crawling around the front of the Suburban
with this line in my hands, I quickly realized that I could straighten the s-curves in one end of the line and add some
bends to the other to make it work. The Isuzu end of the line, however, had the wrong fitting. So, I cut the tip off
this end of the line, slid the stock fitting off, and slid the Isuzu fitting on. I was lucky to have the remainder of the
Isuzu line with the fitting still on it – so I reused it. The lines were very close in diameter, so I figured it would work.
After slipping this onto the pump end of the O’Reilly line, I flared it and bolted everything up.
I still needed a return line and a reservoir. This doesn’t have to be anything special, so I looked for an inexpensive
reservoir online. I found a BMW reservoir on Amazon that sells for $15 and ordered it. I threaded some fittings
into the bottom of it for low pressure hydraulic lines. I also pulled the flanged low pressure connection from the
bottom of the power steering pump, ground off the remainder of the mangled line that was attached, drilled it,
tapped it for NPT, and installed a brass nipple in it. At the steering box, I cut off the old return line, leaving enough
of it in place to serve as a low pressure nipple. Then, I simply ran low-pressure hose designed for power steering
systems. It pays to think through the system: High pressure fluid goes from the power steering pump to the
steering box, then low pressure fluid flows to the reservoir. After that, low pressure fluid flows from the reservoir
to supply the power steering pump.
The lines work great, but I’ve had two issues with the power steering system. The first issue is that late GMT400
Suburbans had speed-sensitive steering using an electronically variable orifice (EVO) in the stock steering pump.
As vehicle speeds increase, this orifice normally closes down, limiting hydraulic pressure and giving the driver more
steering feel at highway speeds. The Isuzu power steering pump doesn’t have this feature. As a result, power
steering is always overkill in this vehicle. It would be a good idea to replace the steering box with one from an
earlier year of the GMT400 Suburban. It appears that the steering boxes from 1992-1995 have a different part
number, and I would expect them to have valving for stiffer feel.
The other issue that I found was that this system appeared to be producing its own power steering fluid. On my
first trip to Colorado I found out that my power steering fluid tank was overflowing. I considered that it wasn’t a
huge tank and that perhaps the fluid was expanding with temperature. I cleaned up the fluid, expecting it to stop,
but it kept providing more goo to make a mess in my engine compartment and on the ground. While spontaneous
generation of petroleum would be a spectacular find, I had to figure out where this additional fluid was coming
from.
It didn’t take long to determine the answer. The power steering pump’s drive gear is on a shaft that extends
behind the engine’s timing cover, where it meshes with the gears driving the cam and fuel injection pump. So, this
gear is exposed to engine oil. Rather than simply pulling fluid from the reservoir, pressurizing it, and sending it to
the power steering box, it was sucking engine oil through the old (probably original, late-80s vintage) seal and
adding it to the power steering fluid. I removed the power steering pump and replaced the seal. While I was in
there, I also replaced the bearing. It wasn’t easy to find the right parts to do this, but some careful research paid
off. The original bearing was marked as an NSK 6204z, which I cross-referenced and replaced with a National 204S
(both have ID=20mm, OD=47mm, thickness=14mm). The original seal was an NOK ae1029e, which I crossreferenced and replaced with either a Timken or National 222050 (I forget which I actually used, but both have ID20mm, OD=40mm, thickness=7mm). These were available at local auto parts stores.
BRAKE VACUUM
Not many consider this issue when starting a diesel conversion, but diesel engines don’t provide a ready source of
vacuum. Automakers have historically relied on having a vacuum source for a number of purposes. In older cars,
vacuum systems were used for just about anything that needed to be actuated, including windshield wipers,
climate control, and headlight covers. In the newest cars and trucks, electric actuation systems are taking over the
roles that vacuum (and, sometimes, hydraulic) systems have historically handled. My 1999 Suburban is getting to
be an older vehicle, but I was surprised to find that the climate control actuators are almost entirely electric (unlike
our newer Jeep Liberty). The vacuum system in this vehicle was only used for two non-engine-related tasks:
operating an actuator controlling coolant flow to the heater core and providing power assist for the brakes.
The Suburban’s considerable size and weight makes vacuum-assisted brakes more than a luxury. Without
functioning brake assistance, this vehicle has unacceptable braking capabilities. The first time I got the diesel
engine running I simply backed it out of the garage to see if I could move the vehicle under its own power. I didn’t
have a vacuum system, yet, so I had no intent to take it out on the road. Even then, I was still surprised at how
scary it was to stop the machine while backing slowly. Do not consider taking one of these vehicles on the road
without power brakes, unless you want to be in a nasty accident!
Though diesel engines like the 4BD1T don’t provide vacuum, accessories are often included to provide it. NPR
trucks from the late 80s used alternators with vacuum pumps built into their back sides. This NPR alternator was
still installed on my 4BD1T when I bought it, but I needed a larger alternator for my application.
When I first had the engine in place and operational, I didn’t have a vacuum system onboard. I assumed that I
could find an inexpensive vacuum pump, and started looking at what was available. I found a small, plastic-cased
vacuum pump used in turbocharged Volvos, but found that it wouldn’t pull enough vacuum quickly enough to keep
up with repeated brake applications in this vehicle. The same pumps are used in some Ford trucks equipped with
diesels, but I doubt that they use them for the brakes. Ganging up a pair of them was still inadequate. I tested this
by hooking things up and monitoring vacuum levels with a gauge, while cycling the brake pedal a few times. It
didn’t look acceptable sitting still in the shop, so I didn’t try this setup on the road.
The market provides a number of options to cover this need. Several companies make vacuum systems for racers.
Many souped-up machines run high-lift cams and/or forced induction systems. As a result, these power plants
don’t produce reliable vacuum for their brake systems. Aftermarket add-on vacuum systems were typically $300+,
so I decided to rig up something myself.
I realized that electric car enthusiasts have the same problem. They are also typically very cost-conscious with
their conversions – while many racers don’t appear to be as concerned. I looked around on the electric vehicle
conversion sites and viewed some of their YouTube videos on the subject. I found that several were using a 12 volt
Thomas Industrial vacuum pump that can be found for $150 on eBay. The model I am using is a 107CDC20-898.
It’s important to note that the 10CDC18-898 has a 10% shorter stroke and won’t move as much air volume – so it
will take more time for that pump to pull a vacuum on the same volume. The 107CDC20-898 does the job quite
well. It moves enough air to keep up, but didn’t come with a vacuum switch to shut it off. I added a separate
vacuum switch so that the pump doesn’t run continuously. I tried several different vacuum switches, but the one
that provides the best value is an adjustable universal vacuum switch that can be adjusted from 6-22 inches of
mercury. It has normally-open and normally-closed connections with adequate current capacity for the pump, and
is apparently used for torque convertor lockup modifications associated with 700-R4 transmissions. I don’t have a
brand or part number to share, but these can be found on eBay for around $30 (search for “6-22 vacuum switch
universal 700-r4,” and you’ll find them right away).
I built a reservoir out of 4” PVC pipe with end caps cemented on. I used hose nipples with ¼ NPT connections.
These were easy to drill and tap into the thick areas where the caps overlap the pipe. I mounted the reservoir on
the vehicle’s right fender where the gasser air intake used to be. I bolted the Thomas Industrial pump to the wall
above the fender using the aluminum base plate that came with it with windshield wiper isolators to minimize the
transmission of pump vibration to the vehicle’s body. I used the normally-closed connection on the vacuum
switch, so that it turns the pump on until the desired vacuum level is reached. The vacuum pump was connected
to a circuit that would be energized whenever the ignition switch is turned on.
After all the vacuum and wiring connections were made (including one for the heater core valve), I turned on the
ignition switch and used the pump’s built-in gauge to observe the vacuum level. I popped the vacuum hose off the
vacuum switch several times, in order to insert an Allen wrench and make adjustments. I tweaked it until the
pump would shut off when it reached 20 inches of mercury. There is some hysteresis in this switch, and it turns
back on when the vacuum drops to about 18 in Hg.
Since I built this system, prices have come down on automotive vacuum pumps, including the Hella Street Vacuum
Pump (#009428087) which can be found for about $150. Enough competition must have hit the market to create
downward pricing pressure, or perhaps the demand for race car parts has decreased in the current economy. This
provides another option if the Thomas Industrial unit ever gives me any problems.
Now I’ve got functional vacuum-assisted brakes. If I did this project over, I would upgrade to a hydroboost system.
Hydroboost provides brake boost using hydraulic pressure from the power steering pump. Others have switched
to hydroboost when performing diesel conversions, and their reports indicate that these systems provide very
confident braking performance. This was an option in the 1999 K1500 Suburbans, so the parts are available. It
would not have been a difficult upgrade to perform, and with my gear-driven power steering pump, there would
be much less to go wrong than with the vacuum system I have set up. Hydroboost also eliminates the large brake
booster diaphragms that take up so much space under the hood. Because this is on the same side of the engine as
the Japanese engine’s exhaust and turbocharger, a switch to Hydroboost also frees up more space for a larger
turbo or even a compound turbo setup.
TACHOMETER
When tuning an engine, knowledge of engine rpm is important. The stock dashboard came with a tachometer in
it, and I thought it would be a shame not to use the stock unit. My philosophy was to perform this conversion in a
way that things looked like they belonged. The problem was that I didn’t have a signal from this engine that
would look like a V-8, providing four pulses for every rotation of the engine. I wanted to use the Hall effect sensor
that came with the engine, mounted in a position where it would signal the passing of 25 teeth for every crank
rotation. I needed a way to downconvert the signal by a factor of 6.25. I looked for some electronic kits online
that would convert frequencies, but didn’t find anything. I wound up using a Dakota Digital DSL-1 universal
tachometer interface. These are designed to read Hall effect sensors reading flywheel teeth or an appropriate
alternator output. I kept the alternator connection in mind as a backup plan, but chose to pursue using the Hall
effect sensor for maximum accuracy.
I had some doubts that I could get the necessary 6.25:1 down-conversion that I needed in this application, and the
DSL-1 was a fairly expensive unit ($70). So, before I permanently installed the interface, I made temporary
connections using test leads under the hood. First, I located the connector that was previously connected to the
5.7’s coil. I connected the white (center) wire to the interface’s output, feeding the tachometer in the dashboard.
I provided +12V to the interface straight from the battery and grounded the negative input. The Hall effect sensor
had two wires, and I wasn’t sure which one I should ground or use as signal. I tried it both ways, finding that it
didn’t matter which way I connected it.
With everything connected, I was able to move the needle on the tach when the engine was running, but I couldn’t
seem to get a ratio that would show reasonable rpms. I realized that I couldn’t get the right ratio when using the
flywheel input on the unit, so I tried connecting the Hall effect sensor to the alternator input on the unit instead.
The displayed rpms were still about double what I wanted, but this was solved by switching from the 8-cylinder
output to the 4-cylinder output. Suddenly, the tachometer showed rpms that were reasonable at idle. The tach
was also moving appropriately with increased engine rpm. Trying the up/down tuning buttons showed that I had
enough adjustment ability to make this system work. I was now satisfied that it was OK to permanently install the
interface.
The DSL-1 isn’t weatherproof, so it needed to be installed inside the cab. The output from the Hall effect sensor
was piped in using the white wire from the coil connector that previously fed the tachometer. When the
instrument cluster was pulled out, I found where that white wire went into the connector and cut it, leaving
enough wire on the connector that I could make a connection there later. I fed the incoming signal to the DSL-1’s
input and fed the DSL-1’s output to the white wire’s location in the connector. I found a great location for the DSL1 in a space just beneath the instrument cluster on the left side of the steering column. This would make it easy to
adjust the output using the up/down buttons on the DSL-1, but the device would be fully hidden when the dash
trim was reinstalled.
Knowing my tire diameters, the differential gear ratio, and that 4th gear is a 1:1 ratio, my spreadsheet showed that
th
the engine would be turning 2000 rpm in 4 gear at 55 mph. Not trusting the speedometer, I used a GPS-based
speedometer app on my Android smartphone, and went for a drive. On a level, straight road traveling at 55 mph, I
simply adjusted the tachometer to read 2000 rpm using the up/down buttons on the interface.
This part of my conversion has been running trouble-free for over a year, and I haven’t had to make any further
adjustments to it. Once it is set up, it can basically be forgotten. It appears that the DSL-1 uses non-volatile
memory to remember its settings, as the tach has stayed accurate even when the battery has been disconnected
for extended periods of time. I’ve only seen hiccups in the tach on two occasions. First, when I had an alternator
issue and voltages were dropping the DSL-1 showed some glitchy behavior. Also, when I have my ham radio
cranked up to 50W in the 2-meter band and key the microphone to talk, the DSL-1’s signal will be lost and the tach
will go to zero. Some added shielding might help, but this isn’t an issue, as it always comes back on as soon as the
transmit key is released.
CRUISE CONTROL
I had expected that installation of the cruise control with the new engine configuration was going to be difficult.
The Suburban was driven to and from Colorado on its first trip there without the cruise control system installed.
The turbocharger upgrade discussed in chapter ten had already been performed when the cruise control was
installed. If I did it over, I wouldn’t have waited so long to add this useful feature.
When I got around to installing this system, I dug the connector out from behind some other wiring harnesses and
mounted the cruise control box in its original location on the firewall. I expected that I would have to remove the
original cable and replace it with a longer one. As I experimented with routing, I was thrilled to find that I could
use the cable with no major modifications. I made a bracket from a piece of aluminum angle with a rectangular
hole in it and bolted it to the throttle cable bracket. The rectangular hole was sized so that the plastic connector at
end of the cruise control sheath would snap into it. Then, I routed the cable across the engine and snapped the
cable sheath into place. The original adapter at the end of the internal cable was cut off and a cable stop was
installed along with a short length of pull-chain (normally sold to extend switches on ceiling fans) that was
connected to the fueling lever. The pull chain ensures that the cruise control can pull but not push on the throttle
lever; avoiding interference with normal operation when the cruise control isn’t active.
One other modification was necessary for proper function of the cruise control system. The stock Suburban had an
automatic transmission and this vehicle now had a standard transmission with a clutch. When cruise control is
used with a standard transmission, use of the clutch should disengage the cruise control – just as using the brake
does. Otherwise, the cruise control will spool up the engine when it is unloaded. For this, I found a clutch switch
for a 1999 K2500 and installed it. The device has a white plastic part that unsnaps and slides off, allowing it to be
clipped onto the clutch pedal pushrod. When clipped on, the white plastic piece is reattached, locking the switch
into place. When the clutch is depressed, a sleeve built into the pushrod slides into the device and this normallyclosed switch opens. The wiring harness wasn’t set up for this, so I spliced it in series with the wire from the
normally-closed side of the brake switch. This matches the normal cruise control setup for a Chevy truck with a
manual transmission. When either one of these switches are opened it cancels the cruise control. It’s important
to use the right connections from the brake switch, because clutch use should not trigger the brake lights.
ELECTRICAL MODIFICATIONS
My philosophy with this diesel conversion was to make things appear and function as close to stock as possible.
I’m not going to go into a lot of detail on all of the minor modifications that were done to make things function
electronically. Some circuits were simply removed. Other connections were simply jumpered to make them
functional. Quite a bit of time has passed, so I don’t even remember exactly what circuits I had to change or
exactly how I did it. Sorry! My bad! Rather than provide the reader with an updated set of electrical circuit
diagrams (which could turn into another book by itself), I’m simply going to provide a series of useful tips when
dealing with electrical systems:
1.
2.
Don’t panic! Take your time with this stuff.
When removing an original system (primarily the gasoline engine), be sure to carefully mark the
connections on the original wiring harness.
3. Delay chopping off connectors or portions of wiring harnesses that seem unnecessary. You may find out
that you actually need to use some of these wires and circuits at a later time.
4. Sign up with a service like Mitchell 1 DIY at www.eautorepair.net, where you can get your hands on the
original wiring diagrams for your vehicle. Be prepared to spend quite a few quality hours learning about
the original circuits in your vehicle as you make things functional after the engine swap.
5. When routing wires, follow existing wiring harnesses as much as possible to keep things neat.
6. Whenever practical, make solder (rather than crimp) connections and cover them with heat shrink tubing.
7. Expect to use lots of convoluted tubing and cable ties to protect your wiring harnesses and keep things
neat.
8. Consider whether vibration might shake your connections loose, and add support to them as necessary.
9. Ensure that new circuits are properly fused, so that nothing melts or starts a fire.
10. When you run into an issue where a system simply won’t work, check to see if an on/off command is
needed from the ECU. You may be able to hard-wire that signal or use a relay to get the desired behavior.
11. Buy some relays and harnesses with normally closed and normally open connections – you are likely to
need a few to create your own simple logic making some systems function properly. I picked up a box of
these on eBay for cheap, and they work fine. They use common connectors that can easily be replaced
with higher quality relays if problems arise later.
12. Consider the reasons for some of the existing logic before making changes. Does a system need to shut
off when the engine is shut off? Could it kill the battery? Does it serve a safety purpose?
OTHER SYSTEMS: CONCLUSION
As I mentioned at the beginning of this chapter, a large number of systems needed to be modified, and those
should not be overlooked when performing a diesel conversion. Many will simply look at what it takes to get the
engine into the compartment – believing that this is the primary set of costs and time. This may be true if you are
replacing one engine with another that was an option in that vehicle. For swapping from gasoline to diesel while
crossing brands, there are a number of details that may be overlooked. By including them in this chapter, I hope
that others won’t overlook the time and expense that will be invested in the many other details of a diesel
conversion.
CHAPTER TEN: TURBO UPGRADE
In the previous chapters I described how I put an Isuzu 4BD1T into a 1999 Suburban. The results were certainly
pleasing, as my Suburban sounded like nothing else on the road (except, of course, for other 4-cylinder diesel
conversions). Because I had bragged about what I was doing, my engineering coworkers kept asking me for
updates. I was finally able to take it to work and show them the results. Yeah, I’m a show-off, but this helps me to
stay motivated with what I’m doing. I topped off the massive 40-gallon tank just before a trip to see some family
in Ohio, and the vehicle achieved a respectable 25 mpg on the highway at 70 mph. The vehicle had enough power
to maintain highway speeds, but I wanted more acceleration.
I had suspected that this installation would initially be underpowered. I chose to try out the stock 4BD1T before
making performance modifications: if it was adequate, I wouldn’t make unnecessary modifications. My suspicions
were confirmed, though, and some performance upgrades were needed.
I got the Suburban running in the summer of 2012 and planned on using it for a family trip to Colorado as the
holidays approached. With a day job and family activities that couldn’t be ignored, the timing would be tight, but I
began my performance modifications.
PERFORMANCE ISSUE
Before I made any changes, I examined what I was experiencing behind the wheel and what my instruments were
telling me.
The high (3.42) gear ratio in the differentials was putting the 4BD1T right at the desired 1900 rpm when traveling
at 70 mph in 5th gear. There was adequate torque at this rpm to maintain speed, and the efficiency was good.
However, the high gearing choice also increased the gap between gears when accelerating. The worst gap was
found when upshifting from 2nd to 3rd gear under maximum acceleration. If the engine is wrapped up to 3,000 rpm
in 2nd gear, an upshift to 3rd drops the engine to around 1,700 rpm. This put the unmodified engine below its
torque band. The engine would slowly build rpms, but the turbo was simply taking too long to spool. This really
hurt drivability and short, uphill highway entrance ramps were something to be avoided. I needed additional
boost and fuel delivery to increase torque at lower rpms. I wanted a solution that would come on early and hold
through the engine’s midrange. Available boost was only around 7 psi, and this number was only seen above
2,000 rpm. Research suggested that the stock free-floating turbo was probably in rough shape. I could have
replaced it, but I knew that better options were available.
I could have started backing out the fuel-limit screw, but I knew that I wasn’t going to reach the desired
performance levels without driving up EGTs and making loads of obnoxious, sooty exhaust. This is inefficient,
impolite to other drivers, and hard on the engine. Making a cloud of black smoke may also attract the muchunwelcomed attention of law enforcement – something to be avoided in an era where a rolling stop can be
rewarded with a rectal exam!
At this point, I had exhausted the budget for my diesel modification effort. It was time to sell our Cherokee. When
we bought my wife’s Jeep Liberty CRD (KJ) a few years before, we kept the Cherokee (XJ) for use as a spare and for
winter driving conditions. With the Suburban, we now had four functional vehicles; excessive with only two
drivers. The XJ had the High Output version of the 4.0 liter inline six, and it never got more than 17 mpg. With big
tires and a roof rack installed, it was currently delivering about 15 mpg. Now I had a much larger, more capable
vehicle delivering economy in the 20s. It was a no-brainer to sell the XJ, upgrade the Suburban’s turbocharger, and
add an intercooler.
TURBOCHARGER SELECTION
Much time was spent staring at compressor maps for turbochargers, wondering where many of the guys on
4BTswaps.com got the data they used to feed their models. I did some simple back-of-the-envelope calculations
to determine reasonable engine flows and conditions. I noticed people installing turbos on Cummins 4BTs and
Isuzu 4BD1Ts that appeared too large for diesels in the 3.9 liter range; unless they were planning to run them
exclusively at high rpms.
A tool that got me pointed in the right direction was Garrett’s Boost Advisor, which is available at
http://www.turbobygarrett.com/turbobygarrett/boostadviser . Versions of this tool are available for Android and
iPhone, but it is also available as JavaScript that can be run in your browser. This tool is straightforward to use. It
collects basic information about the application and the desired performance. It then uses the collected data to
calculate the desired pressure ratio and corrected air flow at the engine’s mid-range and peak rpms. Based on the
results, it provides the user with a list of potential turbochargers. It provides those turbos’ compressor maps with
the engine’s calculated mid-range and peak conditions superimposed on them.
I had heard that the stock injection pump could support up to 250 hp 15. I knew I wouldn’t max out my injection
pump’s capabilities right away, but I wanted to ensure that I would get a turbo that could support reasonable
modifications in the future. So, I entered the following information into Garrett’s Boost Advisor:










Crank horsepower target: 250 hp
Engine displacement: 3.9 liters
Single or twin turbo: Single
Fuel: Diesel (accepting the default air/fuel ratio and brake specific fuel consumption)
Number of valves per cylinder: Two (accepting the default volumetric efficiency of 0.80)
Mid-range engine rpm: 2000
Peak power engine rpm: 3000
Type of intercooler: air/air (accepting the default pressure drop and effectiveness)
Barometric pressure: 14.7 psi (standard day at sea level; entering the zip code would pull in current
barometric conditions)
Ambient air temperature: 80 degrees (using a warm day, rather than the current conditions for my zip
code)
When I originally ran the analysis, the tool provided a list of turbochargers with compressor maps that were in the
right neighborhood, but some appeared to be poor choices. Some showed the mid-range rpm point to the left of
the compressor map. This means that those turbochargers’ compressors would be operating in surge at low and
mid-range rpms. Compressor surge occurs when the pressure ratio is too high for the current air flow. Under
these conditions, the compressor airfoils are operating at a very steep angle of attack, airflow separates, and the
compressor stalls. In this context, the term “stall” means that aerodynamic efficiency has dropped off
precipitously, rather than that the turbo has ceased spinning. Surge operation is seen as fluctuations in pressure
that can shorten the turbo’s life and affect driveability. Surge is generally good to avoid. While writing this
chapter, I ran the program again and noticed two changes in the results. The first is that more turbos are being
suggested, and the second is that a much higher percentage of them appear to be reasonable choices. They’ve
made improvements to the suggestions that it provides.
15
Carcrafter22 Thread entry: Injectors, 4BT Swaps, 8 January 2010.
http://www.4btswaps.com/forum/showthread.php?12356-Injectors&highlight=honed+injectors
With the limited information provided by this tool, I studied and analyzed this subject extensively. I looked at the
valuable experience of others on 4BTswaps.com, and performed quite a few searches to find which turbo models
were readily available on the Web. I wanted a water-cooled turbocharger with a tight (low aspect ratio) turbine
that would spool up quickly at low rpms. I also wanted a T3 flange that would bolt up to my exhaust manifold.
Now that I had a couple reasonable operating points from Garrett’s tool, I looked at all the compressor maps that I
could find on 4BTswaps.com. Once again, I found that that many of the larger turbos recommended would be
operating in surge at my mid-range condition. With high aspect ratio turbines, surge might be avoided by using
“loose” turbines that delay boost until higher rpms were reached – but this would defeat the purpose of my turbo
upgrade. Some of these larger turbos might be good candidates for compound turbo applications, but I wanted to
minimize complexity and cost.
I found a rebuilt GT2259 from a Hino truck for around five hundred dollars on eBay. The GT2259 was one of the
best options provided by the Garrett tool, and I researched it further. I couldn’t find anybody who had used this
turbo on any of the 4BD or the 4BT variants. When I asked around, several of the experts seemed to think this
might work quite well. Though the Hino truck turbo was described as a GT2259, I realized that there could be a
number of differences in an OEM part. Dougal had already pointed out that while this turbo’s T3 flange was
rotated 90 degrees and would require an adapter to function in my application16. Before I made the purchase, I
performed one last sanity check.
The Hino truck that this turbo comes from is a 155 COE, a cab-over truck with a 14,500 GVW; very similar to the
Isuzu NPR truck that my 4BD1T came from. This Hino truck is powered by J05E, which is a five liter, 4-cylinder
diesel producing 210 hp at 2,500 rpm and 440 ft-lb at 1,500 rpm. 17 If one simply scales displacement from 5.0 to
3.9 liters, the ratio is 1.28. I assumed similar volumetric efficiencies and scaled the 5.0’s maximum horsepower
point of 2,500 rpm by this ratio. If my assumption held true, similar exhaust and inlet flows might be seen from a
3.9 at around 3,200 rpm. So, there’s a reasonable comparison between the engines, as the stock 4BD1T produces
its maximum horsepower at a little over 3,000 rpm. Scaling the Hino’s maximum torque rpm of 1,500 by this same
ratio takes us to 1,920: in the range where a 4BD1T makes its maximum torque. So, a quick sanity check showed
that these two 4-cylinder engines were actually quite similar in terms of use, and that mounting this turbocharger
on either engine would result in similar flows to and from the engine. The higher output of the JO5E promised a
turbo with good capacity for increasing the 4BD1T’s performance. The Hino version of this turbo was also watercooled and designed for the abuse that these medium-duty commercial trucks receive. The price was reasonable
and this was a good turbo to try.
I ordered the GT2259 with a number of other components to begin work on my upgrade.
16
Dougal Hiscock thread entry: GT2259, 21 August 2012.
http://www.4btswaps.com/forum/showthread.php?24268-Gt2259
17
Hino Trucks 2012 HINO 155 COE, sales brochure.
INSTALLATION
For oil and coolant to flow through the bearing housing and drain properly, the turbocharger’s shaft needed to be
mounted horizontally. In order to make plumbing easier, it would be best if the inlet to the compressor housing
was pointed away from the Suburban’s firewall. The T-3 flange on the turbo was oriented vertically, while the T-3
flange on my exhaust manifold was oriented horizontally. To fix this, I purchased a pair of T-3 flanges on eBay,
clamped them back-to-back at a 90° angle, marked them with a permanent marker, unclamped them, and started
grinding transitions for smoother exhaust flow. When I was satisfied with the shape, I had them welded together
with beads on the inside and the outside. Then, I ground the inside beads to make them smooth.
The custom adapter at the exhaust manifold would allow the turbo’s shaft to be horizontal, but I still had to rotate
(clock) the bearing housing relative to the turbine and compressor, placing the oil drain on the bottom. Before
unbolting the turbine or compressor housings, I used a straightedge and a permanent marker to mark their
positions relative to each other. Normally, the relative positions of these housings don’t matter, but this turbo has
a wastegate actuator mounted on the compressor housing. For the actuator’s pushrod to reach and properly
control the wastegate’s bell crank, the relative geometry needed to be maintained. With the markings in place,
the housings were unbolted and removed. Normally, they can simply be loosened and rotated, but I chose remove
both housings to take measurements that I could share. The measurements I took are below. Most confirm the
specifications I’d seen before I purchased this turbocharger.
Measured turbine characteristics



Inducer: 50.3 mm
Exducer: 43.2 mm
Aspect ratio: 0.47 (stamped on the housing)
Measured compressor characteristics



Inducer: 42 mm
Exducer: 59.4 mm
Aspect ratio: 0.61 (stamped on the housing)
I was surprised when I saw such a low aspect ratio on the turbine housing. I had expected a larger number, but
this tighter turbine would result in more boost and torque available at lower rpms – which is exactly what I was
looking for.
Before I purchased the turbo, I realized that the collector flange didn’t appear to match any standard Garrett type.
Hino appears to have their very own custom flange design for this turbo, and I never found a match anywhere
online. I saw quite a few Garrett collectors out there, but I could see that none of them had the right bolt pattern.
So, I had to build my own collector. I used some leftover 3/8” steel plate that was used elsewhere in this
conversion. I traced the rear flange shape onto the plate, cut it out, and pulled out an exhaust elbow made from
3” tubing. There wasn’t enough room in the plate for a full 3” circle to be cut out, so I determined the ideal elbow
orientation relative to the plate and “ovalized” it in my bench vise. Then, I traced this onto the plate and cut it out.
I realized that the wastegate couldn’t open properly with a flat plate, so material was ground away behind the
wastegate to make more room in that area.
As I had done with the previous turbocharger, I drilled and tapped the turbine inlet, allowing the installation of my
EGT gauge’s thermocouple.
As I was upgrading my turbo I added an intercooler to maximize the benefit of my upgrades. The Suburban didn’t
have much room available between the radiator and the grille, so I looked at other options. I considered putting a
scoop in the hood and mounting an intercooler on top of the engine. Subaru WRXs do it this way, but I didn’t want
to cut nice sheet metal or purchase a fiberglass hood. Rod Brace had said something about hanging the
intercooler on his Suburban behind the bumper, so I examined that option. I took some measurements and found
that an MR2 intercooler would fit fine in this location. I purchased one on eBay, mounted it behind the bumper,
and cut a hole in the bumper to provide airflow. Eventually, I will build a plastic duct to help direct that airflow and
a small grille to keep roadkill from plugging the intercooler’s fins – but I still haven’t. From some experimentation,
I found out that using this intercooler only creates a 1 psi pressure drop, and it assists in maintaining safe EGTs.
I finished the installation using pieces of aluminum tubing and silicone elbows that I purchased on eBay. I got
creative determining a path from the intercooler to the intake manifold, and the best path turned out to be one
that passed under the air conditioning compressor and the belts that drive it.
RESULTS
After upgrading the turbo and adding the intercooler, the results were immediate and noticeable. Normal upshifts
will happen when the engine reaches 2,500-2,800 rpm, putting the engine at around 1,500 rpm in the next gear.
With this setup, boost is available immediately, providing 10 psi at 1,400 rpm, and reaching the wastegate-limited
maximum of 15 psi at around 1,700 rpm. The engine pulls well up to 3,000 rpm, when it seems that the turbine
must be choking. It might be nice to get some useable power above 3,000 rpm, but I really like having all that
torque available at lower rpms. Perhaps I will eventually build a more efficient collector and port the wastegate,
but I’m quite happy with this setup as it is.
In order to make full use of the available boost, I gradually backed the fuel screw out all the way. I backed it out a
little at a time and tested under a variety of conditions. The EGTs never got above 1,100°F, even when I finally
backed all the way out. I also unscrewed the aneroid, removed its pushrod, and reinstalled it. I was surprised how
much this step improved drivability. After this modification, I found out that the nipple on the aneroid was leaking
fuel, so I mixed up some JBWeld and plugged it.
With no further modifications, I can make a little bit of black smoke if I try hard enough, but it cleans up quickly
and isn’t too noticeable near sea level. It’s no worse than my wife’s near-stock Liberty CRD, and not even close to
the cloud I can produce with my retuned Jetta TDI. On my last trip to the Colorado Front Range, however, I had to
ease off on the throttle at low rpms. The 3 psi decrease in ambient air pressure at 5,200 ft above sea level is
enough to cross a threshold, allowing substantial black cloud production. I should point out that the purpose of
the aneroid is to limit fueling at high altitude, but the overall improvement at sea level outweighs this. After
seeing some recent information that Dougal shared with me (and is shared below), I will be adjusting the
wastegate to maximize my output – which will also clean up the exhaust at high altitudes.
Shortly after the upgrade, I had some questions about whether the wastegate was truly the limiting factor on
boost pressures, so I temporarily disconnected the hose from the compressor housing and capped off the nipple. I
found out that this turbo would very quickly reach 25 psi any time I floored the fuel pedal. I also noticed that
allowing the boost to go this high didn’t help with performance, so I reattached it and have left the wastegate set
at 15 psi. I hadn’t backed out the fuel-limit screw or removed the aneroid pushrod at that time, so I will be
revisiting what increased boost can do for drivability and performance.
The Suburban isn’t going to win any drag races, but these modifications do allow the vehicle to accelerate more
effectively. The improvements allow more confidence when pulling out into traffic and eliminate the need to
downshift for hills. More power would always be nice, but this vehicle is no longer limited by how much air can be
delivered.
MORE TECHNICAL INFORMATION
As I was wrapping up this book, I was on the 4BTswaps.com website and saw some really useful calculations that
Dougal was assembling. He’s been looking at what can be done with the GT2259 on the 4BD1T with an intercooler
and the maximum fueling that the stock injection unit will provide. When I asked him about it, he agreed to let me
share some information here.
To reach a maximum of 245 horsepower, his calculation of the expected air flow versus pressure ratio winds up
pushing to higher pressure ratios than what the Garrett calculator generated when I targeted 250 hp. Garrett’s
tool doesn’t know the specifics of this engine, and I used a number default values when setting up the tool. Dougal
has put a lot of time into this effort, and I would put more weight on the curve he is providing here. When his
curve is overlayed with the GT2259 compressor map, it can be seen that the turbo and this engine are pretty well
matched. As off-idle rpms and boost increase, the curve stays on the safe side of the surge line. I can confirm this,
as I’ve never seen or heard any evidence of surge. Maximum horsepower is reached at a point that goes outside
the map at the upper right corner. Without a properly instrumented dyno test, it is hard to know how accurate
Dougal’s curve is or if the turbo could keep up under these conditions. However, this clearly illustrates that this
turbo would provide excellent performance for the engine’s low and mid-range. The results reinforce the idea that
this turbo was a good choice. A number of other turbos for the 4BD1T have been examined by Dougal in his
incredibly useful thread here: http://www.4btswaps.com/forum/showthread.php?26542-4BD1T-Turbo-Sizingand-Performance-Prediction, including the HE221 and the TD04HL-19T. If somebody is looking to increase fueling
beyond what the stock pump can provide, they will clearly wish to look at some of these other choices. Dougal
also overlays his pressure ratio versus air flow curve with a number of other turbos, showing agreement with my
observations: some of the popular “upgrade” choices are not good picks for this engine.
Compressor maps don’t illustrate the role the turbocharger’s turbine plays in resulting engine performance and
transient behaviors. A “tighter” turbine will have a lower aspect ratio number and will spool more quickly at lower
engine rpms. At higher rpms, tighter turbines will tend to choke and limit the engine’s maximum output. Some
relief on this restriction is offered on wastegated turbos, which allow exhaust gasses to bypass the turbine as the
wastegate actuator’s maximum boost setting is approached and the wastegate opens. Wastegates allow smaller,
more responsive turbines to be used, with smaller sacrifices for operation at higher rpms. 18 The Hino version of
the GT2259 uses a turbine with a very tight 0.47 aspect ratio, which makes it spool very quickly to provide the
great low rpm torque that my Suburban needed. A number of other applications use different aspect ratios,
including the 0.56 aspect ratio that Dougal used in his performance models. The following results were modeled
by Dougal using a GT2259 with a 0.56 aspect ratio. Note that these predictions are well-grounded in theory, but
no dyno tests have been performed to confirm the results. They use the stock injection pump’s maximum output
and allow the GT2259 to provide up to 26 psi of boost.
18
Dougal Hiscock email: The Art of Diesel: Chapter Ten, 31 December 2013.
The results are quite impressive, as the engine produces almost 470 ft-lb of torque at 2,100 rpm, and reaches a
peak output of 245 horsepower at 3,300 rpm. I’ve limited my boost to 15 psi, but I can confirm that the GT2259
spools quickly and I never lack torque from the 1,500 rpm to the 2,500 rpm range. After that, my engine’s
performance falls off rapidly. This may be caused by my boost limitation, and Dougal’s results have convinced me
that I need to perform further experimentation with my settings.
NEXT STEPS
I’ll continue experimenting to see if I can get more torque and horsepower out of this engine. From Dougal’s
calculations, it appears that I’ve unnecessarily limited the available performance of my engine by limiting the
boost. With my Hino GT2259’s tight turbine, I may not reach the maximum horsepower figures that Dougal
predicts, but I’m convinced that I can get more mid-range torque and more horsepower below 3,000 rpm. I’ve
recently threaded the rod on my wastegate actuator, and will begin experimenting with boost pressures to see
how much improvement is available. I may also consider porting the wastegate to allow more flow and building a
more efficient exhaust collector as steps to improve the engine’s top-end performance.
The Suburban’s current fuel economy is impressive when compared to stock figures. I consistently see 26 mpg at
70 mph when traveling on the highway. When traffic once forced me to travel at a lower steady speed, fuel
economy reached 27 mpg. In mixed driving I see 22-23 mpg, which isn’t bad, either. I still believe I can get 2-3
more miles per gallon by tweaking the injection timing. Before I installed the engine I set the timing to the
specification found in the manual, and I intend to begin experimenting with this next. I would like to reach 30
mpg, but that might not be reasonable with a vehicle this heavy and with this much frontal area. Further
experimentation to improve fuel economy may include some aerodynamic improvements, such as vortex
generators and a belly pan.
WHAT I’D DO DIFFEREN TLY
Based on what I know right now, I think I picked the right turbo for my application and I would use the same one
again. However, more may be learned in the future. For anybody who performs a similar upgrade, I recommend
visiting 4BTswaps.com and visiting Dougal’s thread 4BD1T Turbo Sizing and Performance Prediction (again:
http://www.4btswaps.com/forum/showthread.php?26542-4BD1T-Turbo-Sizing-and-Performance-Prediction) to
find the latest information. Dougal is using proper engineering methods to fit turbos to these engines and predict
performance. As more is learned, it will certainly be shared there.
CHAPTER ELEVEN: OTHER IMPROVEMENTS
This book has been written primarily to show how the 1999 Suburban was fitted with a 4BD1T to make it a
functional, efficient family hauler. The vehicle I chose was rust-free and in excellent condition, but after putting so
much effort into the diesel conversion, I wasn’t going to settle for a number of other things that just weren’t right
with this vehicle. Some of the improvements that follow were driven by the diesel conversion, but others are
simply the result of choosing a GMT400 platform.
BRAKE PROPORTIONING
This was not caused by the conversion, but the Suburban’s stock braking system really left a lot to be desired.
When purchased, the Suburban it made a highway trip from where I bought it to my home. Once there, it was
pulled into my workshop and promptly disassembled. I didn’t have much opportunity to assess brake function.
When I got the vehicle running under diesel power with my homebrewed vacuum system installed, I thought that I
had somehow managed to screw up the brake system. Some improvement was found after swapping the master
cylinder, the booster, both rear slave cylinders, and all three rubber lines, followed by much time bleeding the
brake lines. It’s important to note that when the brakes are bled on GMT400 trucks using manual methods, ABS
must be activated to expel air that may be trapped in the system. If one has thousands of dollars invested in
dealer-type diagnostic equipment, the ABS can be activated with a few keystrokes. For me, repeated hard stops
on gravel helped the bleeding process and firmed the pedal feel, but the brakes were still unacceptable.
Research on this issue showed that these vehicles were shipped with proportioning valves that apply a heavy bias
toward the front discs. The stock proportioning was so exaggerated that owners claim the rear drums don’t selfadjust and the rear shoes never wear out. I heard that a later version of the proportioning valve had fixed the
deficiency, so I made the swap. Braking was instantly improved, but I found that the bias was now too far to the
rear. Emergency braking would immediately make the rear tires chirp before the ABS kicked in. If I continued
emergency braking to a complete stop, the vehicle would lurch multiple times as it slowed; showing that the
proportioning was outside the limits of what the ABS system could correct. It certainly pays to try these things out
on back road with no traffic! Not only is weird vehicle behavior an embarrassment, but getting rear-ended will
certainly ruin your day! This is especially true when you have a lot of time and money invested in the vehicle. In
addition to testing the system in a place with no traffic, it is best to make several braking runs at increasing levels
of effort – so that problems can be found without any dangerous surprises.
Stock braking systems generally allow full line pressure to the front brakes and limit the pressure provided to the
rear brakes. In my case, changing proportioning valves simply changed the level of allowable rear brake pressure.
The original allowed almost no pressure in the rear line, while the new one allowed too much pressure. To solve
this, I added my own racer-style adjustable proportioning valve to the rear line, allowing me to further reduce the
rear line pressure to an adjustable level. With further experimentation, I got the brakes properly proportioned.
TIRES
When I was working on the Suburban I noticed that the tires were mismatched and in need of replacement. For
some reason, the tires were also smaller than the stock size of 245/75R16 that supposedly came on these vehicles.
I wanted tires that were taller than stock in order to reduce the engine revs to a targeted 1,900 rpm at 70 mph.
Spreadsheet calculations showed that 265/75R16 tires would achieve this target, when combined with 3.42 gears
and the NV4500’s overdrive ratio. So, I priced tires this size with good traction capabilities from a number of
sources.
One source included Goodyear Assurance FuelMax tires as one of their low-priced options. When I saw the
FuelMax label I was immediately suspicious of how tires could achieve low rolling resistance while still being mud
and snow rated. These tires also managed to receive an “A” rating for traction. I searched for more information
and found a YouTube video created by Goodyear that explains their approach. Rather than simply putting hard
rubber in the tires and suffering the consequent loss of traction, Goodyear uses a tread compound that doesn’t
turn as much of the energy used to flex the tire into heat. If one looks at a piece of rubber as a spring and damper
system, it’s like the damper’s constant has been reduced, while leaving the spring’s value alone. In a spring and
damper system, springs store energy in a conservative manner, giving back the energy. Dampers, however, turn
movement into heat. This is what shock absorbers do – as absorbing energy makes things less “bouncy,” and helps
keep tires in contact with the road. The result, in Goodyear’s video, is that identical rubber balls made of their
compound roll more easily than rubber balls made of normal tire compounds19. Because the price was good and
this was a fuel economy project, I decided to give these tires a try.
I found out that these tires had good traction and I had no complaints with that aspect. However, I had a handling
issue that I was trying to sort out. I thought I’d sorted out the other potential causes, and decided to put another
set of tires on it. I chose the Fuzion SUV tires for a good price and excellent reviews. They also have great traction
and are mud and snow rated – though they look more like street performance tires. My switch to the Fuzion tires
fixed one subset of my handling problems, which was that they didn’t tend to follow grooves on concrete the way
that the FuelMax tires did.
19
Goodyear video: The Science of the Assurance® Fuel Max® Tire, Goodyear Tire, 15 March 2010.
http://youtu.be/qXVsEBT9G-Q
These FuelMax tires were not the cause of my primary handling issue, though. Making the switch did confirm that
the FuelMax tires had a positive effect on fuel economy. The Fuzions measured in at the same diameter at just
over 31”, but I lost 1-2 mpg, depending on conditions. So, I’d recommend the FuelMax tires for fuel economy.
There seem to be a number of reviews complaining about their handling and some quality issues, but the FuelMax
tires were not the cause of my Suburban’s handling problem.
It could be that I need to upgrade to some heavier truck tires that take higher pressures and have stiffer sidewalls,
but I’m still diagnosing what the issue is on this vehicle.
HANDLING
I’ve mentioned a handling issue in the previous section, and this is worth further discussion. At speeds up to 65
mph the Suburban doesn’t seem to have any issues. When it is loaded down with people and gear at speeds of
70+ mph, it starts to get squirrely. It feels like the rear end of the vehicle wants to walk around. Lane changes and
course corrections have to be made slowly and carefully, or oscillations in the yaw axis can be set up.
I assumed that old, worn-out rubber bushings were the cause. My first upgrade was the installation of a full set of
polyurethane bushings. That took two weekends of work and had little/no effect on the issue.
My next upgrade was to put a large diameter sway bar on the rear end, thinking that I was getting some swaysteer from the spring angles. Again, this didn’t fix the issue.
The rear springs didn’t appear to have sagged on this vehicle, so I dismissed those as a potential issue. After my
last trip to Colorado, I decided that this might actually be a problem, though. So, I took the cheapest available path
to stiffen up the rear end to troubleshoot the issue. I installed some Gabriel Hijackers that are air adjustable.
Putting 80 psi in these picked up the rear of the Suburban and noticeably increased the spring constant in the rear
end. Once again, I found that I hadn’t fixed the problem. However, it is possible that these tired old springs lack
stiffness in side-to-side movement and I may still need to replace them.
1999 Suburban handling problems can be found in a number of sources online. These vehicles shipped with an
electronic variable orifice (EVO) system mounted on the power steering pump. This is part of a speed-sensitive
steering system that decreases the hydraulic pressure provided to the steering box as vehicle speeds increase.
This increases driver feel at higher speeds. The complaints stem from a sensor in the steering column that wears
out, resulting in erratic EVO behavior that changes driver feel while in the middle of maneuvers. This is a
dangerous issue that should be watched, but this is not the issue with my Suburban. I’m using the 4BD1T’s geardriven power steering pump which is not equipped with an EVO. However, I do have full-blast power steering at
all times, and driver feel is reduced at highway speeds. This isn’t the first vehicle with hyper power steering that
I’ve driven, though, and I don’t believe that this is the full explanation for my handling issue. I believe that
swapping the steering box with one from an earlier, non-EVO model year may help, though. I may consider
purchasing a racing version of the steering box with high gearing that has been set up to maximize driver feel at
high speeds, but I’m not ready to spend another $400. Not yet.
I may have found a genuine contribution to the real handling issue, however. I looked at the build codes on the tag
in my Suburban’s glove compartment, and found out what torsion bars it was equipped with. It came with the
bars bearing the GF code that have one of the lightest load ratings available. Their maximum torque rating is only
5,826 ft-lb. The combination of soft torsion bars and a few hundred pounds of weight in the vehicle’s front end
(the engine and the transmission are both heavier than stock) may be contributing to the issue. The front end may
have sagged, but my first alignment involved setting the ride height back to stock, as the torsion bars had been
removed during the conversion. Any front end sag resulting from the addition weight was certainly masked by
setting the adjusters. The spring rate of these bars remains as it was, however, and some lighter trucks came with
stiffer bars than these. I found a set of bars with the GG code in a local salvage yard. These have a higher max
torque of 6,707 ft-lb20 (15% higher than the GF bars), and they seem to have helped the issue without making the
ride too stiff. I’m not done, though, and may still increase the stiffness by another step or two.
OTHER OTHER IMPROVEMENTS
The GMT400 is known for a number issues, including tail light electrical boards that go bad and front door handles
that eventually break. For any platform that you choose with a conversion, those problems are likely to remain.
20
GMfullsize.com, GM Torsion Bar 401, http://www.gmfullsize.com/tech/torsion401.html
However, in common vehicles the problems are well-known, parts are available, and the Web is filled with “How
To” articles and posts describing causes remedies for any common problem.
The headlights are known to get hazy on these vehicles. I tried polishing them, but the lenses were yellowed from
sunlight and they still looked awful. I picked up a set of headlights and marker lights from Amazon for $70 that
matched the originals but were nice, fresh, and clear. It really improved the vehicle’s appearance, and I’ve actually
received comments on having nice-looking headlights. People are used to seeing cloudy, yellow lights on these
vehicles.
I built a custom set of floor mats for the vehicle. Super heavy-duty floor mats and liners for the cargo area can be
made from the liners used for horse stalls. I found mine at Rural King, but I’m sure that other farm supply stores
have similar products. These are easy to cut and fit into place. They are much thicker and cheaper than readymade options, and the cost effect is even more important when you are protecting the floor for three rows of
seating and a sizeable cargo area.
I also built a custom set of mud flaps. Like floor mats, I noticed how much automotive accessory places ask for
dinky little mud flaps that are primarily a fashion statement and do little to protect a vehicle’s body panels. At
Rural King I found a single large truck mud flap for $15. I chopped it into four equal sections that were just the
right size to make a very thick, durable, effective set of mud flaps for my Suburban.
WRAP UP
If you do a conversion such as mine, you will have invested a sizeable chunk of time and money in the effort. You
will want to consider a number of improvements that will keep your vehicle on the road for a long, long time.
While many see vehicles as disposable items, a diesel-powered machine has the potential for a very long service
life if it is cared for properly. I could go on endlessly about inexpensive improvements that could be made to a
modified Suburban or almost any vehicle. However, I don’t have many unique ideas to share in this area. Anybody
that modifies a vehicle will likely have their own ideas about how to make their vehicle drive well, handle nicely,
brake securely, and look good.
CHAPTER TWELVE: WHAT’S NEXT
The Suburban has come a long way but will continue to improve over time. I want to continue sharing progress on
this and other projects. You’ll always find updates on this vehicle and other practical self-reliance projects on my
blog:
http://theartofdiesel.com/
I will also post updates from time to time on my YouTube channel: Mark-A-Billy:
http://www.youtube.com/channel/UCX0o8OVAH4G0S1L_MVeYP-g
The next improvements to the Suburban are likely to include:
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Handling: As I break the code on why this thing is so squirrely, I will share my answers and whatever
changes are necessary to make it handle as it should.
Fuel economy: I will start optimizing the injection timing and other variables to increase the Suburban’s
fuel economy. Aerodynamic improvements are likely to be a part of the process.
Performance: Even as I upgrade the fuel efficiency of this vehicle, I plan to make it more capable and fun
to drive.
Mobile power generation: I’m considering outfitting the Suburban so that it can be used to power my
house when the grid is down or to run power tools in remote locations.
I will also cover maintenance and modifications on my 2001 Jetta TDI and my wife’s 2005 Liberty CRD. Now that I
have a fleet of three diesels, there’s more to play with!
Non-automotive engineering & self-reliance projects that I’m considering include:
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A flying home surveillance system with infrared capabilities.
A monitor for my backup sump pump that sends email alerts for power outages and lets me know when
the backup sump is operating.
Amateur radio systems for family communications.
The use of alternative fuels for power equipment.
I support my wife and children in the pursuit of their self-reliance projects, so I’ll provide my non-expert updates
on:
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Raising chickens, rabbits, bees, and other livestock that we may add.
Gardening and (perhaps) permaculture.
A rocket stove mass heater for my basement.
http://theartofdiesel.com/ will concentrate on the practical side of liberty. I will touch on philosophy, but this site
will concentrate on actions that one can take to live well in trying times. If you are interested in reading more
about current events and philosophy as seen through the eyes of a hardcore libertarian, I’ve set up a second blog:
http://core4liberty.com/
The name Core for Liberty is based on the idea that everybody has a desire for freedom deep in their heart,
whether they realize it or not. It’s a part of human nature; it’s an inherent part of who we are and how we behave.
Topics that will be covered on this site include:
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Current events.
Defense of the United States Constitution and the nullification of unlawful federal acts.
Issues with main-stream education and alternatives that can be pursued.
Issues with the Federal Reserve, monetary policy, and legal tender laws.
How Christianity and libertarianism can work together to form a consistent, moral worldview and
philosophy.
How you can do your part to stem the continued growth of government.
I hope you enjoyed this book! Please contact me with feedback and questions related to this book via this email:
[email protected]