3000GT/Stealth Bellhousing Brace Installation

3000GT/Stealth Bellhousing Brace
Installation Guide for W6MG1 6-Speed
Manual Transmissions
Submitted by r1elkins
Additional information provided by Armond30 and lethal_vr4
1.
Remove transmission. At this point, if you don’t know how to remove
the transmission, then stop this project altogether and pay a
professional to do it.
2.
Remove the (2) 12mm bolts that hold the Gear Select Lever in place
and remove the lever. See Figure 1.
Figure 1
3.
Remove the Reverse Shift Detent (24mm), Guide Bolt (13mm) and
Shift Detent (22mm). Note: the Shift Detent is spring loaded, so be
cautious when removing it so you don’t loose the spring. See Figures
2, 3 and 4.
Figure 2
Figure 3
Figure 4
4.
Remove the Shift Shaft by unscrewing the (4) 10mm bolts. Pulling
the shaft out is easy to do if you have the transmission in neutral.
You can tell that you have it in neutral if you can move the shaft up
and down freely. If not, rotate the shaft back to the center and you
should be able to move it up and down. Note: the Shift Shaft has a
spring at the end of it. If you pull out the shaft and don’t see the
spring attached to the end, don’t worry. It is lying inside the
transmission at the bottom and you can easily pull it out. See Figures
5 and 6.
Figure 5
Figure 6
5.
Now you are ready to remove the (17) 10mm bolts that hold the
Clutch Housing to the Center Case. Note: there is (1) 10mm bolt
located inside the housing where the clutch is located and there are
(2) on the bottom of the transmission. These (3) bolts are in the
opposite direction of the other (14) bolts and are easy to miss. See
Figures 7, 8 and 9.
Figure 7
Figure 8
Figure 9
6.
Now the housing is ready to be removed. Place the transmission on
the Rear Cover with the Clutch Housing facing up. Use a rubber
mallet and break the static bond of the housing and the case. This
might require using a pry-bar to fully unseat the housing from the
dowels, but only a little force is necessary. If you have to use more
than a little force, then you have missed a bolt somewhere (it does
NOT require heavy pounding or the use of your body weight to pry
the two apart). Use common sense and take your time. Once
removed, it should look like Figures 10 and 11.
Figure 10
Figure 11
7.
Figure 12 illustrates how the brace is going to be installed. Some
machining/grinding of the housing and the brace is required before
the brace can be welded in place. Again, this is just for illustration
purposes only.
8.
Figure 13 shows the areas that need to be machined/grinded off the
housing for the brace to sit correctly. If you compare Figure 10 to
Figure 13, you will see the four areas that need machining/grinding.
I machined these areas flat with the housing’s surface as you can see
in Figure 13. If you do not have access to a mill, a pneumatic or
electric angle grinder will also work. Just make sure you have a
steady hand and go slow.
Figure 12
Figure 13
9.
After you have machined as much material off the housing as possible,
now it is time to fit the bracing into the housing. The brace should
fit nice and tight, and should require a bit of force to make it fit.
You want a slight interference fit. This puts a bit of preload on the
whole setup which will make the entire thing stronger. If you have a
slight pinch on the top and bottom of the bearing races (squeezing
them together) and a slight pinch on the top and bottom of the
housing (plate pushing on them) that gives enough pre-load to
prevent fatigue fracture failure. If you grind the brace so that it falls
into place, then the strength of the brace will come from the welds.
The welds should not be where the strength comes from, the
interference fit and the strength of material should be the source of
the brace’s strength. You also want to maximize plate width as much
as possible, meaning, in areas where it gets narrow like between the
shift rails and the output shaft, take as little material off as
necessary. That way, your heat affected zone from welding doesn't
stretch the whole length of the plate and weaken the whole thing.
Plus, ensuring that there are no sharp edges on the plate or the bell
housing will reduce the chance of future cracks as well. It's pretty
complex to get it perfect, but almost anything is an improvement
over the stock casting. If the brace does not lay flat on the housing
after you have forced it into place, you will need to sand/grind/mill
down the brace where there is too much interference. Try using wet
sandpaper first and see if that does the trick. If not, then proceed to
using other methods. Once you have done this, the brace should fit
nice and tight and sit flush against the housing. My interference
came from two places. The brace was interfering with the upper
part of the housing too much and was wedging itself as I pushed down
on it, and the radius of the brace that goes around the output shaft
bearing race was a bit too small. A light wet sanding of both areas
and the brace could be forced into place and was nice and tight. See
the blue highlights in Figure 14 of the areas of the brace I had to
sand. Thanks go to Armond30 for the previous explanation in
strength and mechanics of materials.
Figure 14
10.
Note: lethal_vr4 mentioned in one of his threads that he had to
clearance two areas of the brace. Figure 15 illustrates these two
areas. It was suggested that having these two areas radiused would
provide adequate clearance. It did for the shift rails, but not for the
ring gear. The left side had to be milled a second time to clear the
ring gear. The way to do this is; radius theses two areas of the brace
first, place the brace in the housing, then test fit the cover. If the
cover does not seat onto the housing with ease, take it off and see
where there is contact on the brace. Continue machining off
material on the brace until the cover and housing fit together with
ease. Figures 16, 17, 18 and 19 show the clearance issues and the
final machining of the brace. Note: unfortunately, I welded my
brace in before I figured there were clearance issues with the cover.
I had to machine the brace while it was installed in the housing.
Figure 19 shows the correct clearance for the ring gear and was
taken after the brace had already been welded into place. While
some pictures from here on out show the incorrect clearance for the
ring gear (EG Figure 21), Figure 19 shows the correct clearance
needed for final installation. (What does this mean? Ignore any
pictures that show the incorrect clearance for the ring gear after
Figure 19. Figure 21 was used to illustrate a proper welding bead,
but it also shows the incorrect clearance…make sense?)
Figure 15
Figure 16
Figure 17
Figure 18
Figure 19
11.
Now that the brace fits correctly and all clearance issues are
resolved, it’s time to weld the brace into place. If you don’t know
how to weld, then I suggest you hire a professional to do it. Figure
21 shows a proper bead that should be expected. When it is done, is
should look something like Figure 22.
Figure 20
Figure 21
Figure 22
12.
Once the brace is welded into place, make sure to grind down any
welding high spots or any areas that might cause interference when
reinstalling the cover.
13.
Before reinstalling the cover and housing, make sure you clean both
gasket surfaces thoroughly. I used a razor blade to scrape any old
sealant off the surfaces and wipe it down with a rag that is soaked in
brake cleaner to remove any oils that could hinder a good seal.
14.
Armond30 recommend the use of Loctite 518 sealant for the housing.
My local Napa store does not carry the Loctite brand, but Permatex is
Napa’s brand and is made by Loctite. Permatex’s equivalent to
Loctite 518 is Permatex Anerobic Gasket Maker. Anerobic means that
it only seals in the absence of oxygen. What does this mean? The
only part of the sealant that hardens is the sealant in-between the
two surfaces under pressure. This way, you don’t have hard chunks
of sealant falling off into your transmission and causing internal
damage. The excess sealant that oozes out when you torque down
the cover and housing bolts just remains in a gel form and won’t
harm anything. See Figure 23.
Figure 23
15.
Reinstall Clutch Housing and Rear Cover per instructions (included in
the Appendix) and torque bolts to spec. When reinstalling the Shift
Shaft, make sure the Rail Lugs are all aligned in the centered position.
If they are not, just use a screwdriver to put them in the correct
position. See Figures 24 and 25.
Figure 24
Figure 25
16.
Use a bit of grease to hold the spring in place on the end of the Shift
Shaft to prevent it from falling during installation. Check to make
sure that it is installed correctly by feeling for tension as you move
the shaft up and down. See Figure 26.
Figure 26
17.
Align the shaft in the neutral position as seen in Figure 27. Use the
same gasket maker as before to seal the Shifter Plate to the
transmission. The shaft should just slide into place with little effort.
Again, check to make sure the spring did not fall off during
installation by moving the shaft up and down and feeling for tension
from the spring. Ensure the Shifter Plate is aligned properly on the
transmission (one corner of it is radiused, and it only goes on
properly one way). Failure to do so will cause the plate not to be
seated correctly and the shaft will be misaligned.
Figure 27
18.
When installing the Gear Select Lever, make sure that the arm goes
below the Shift Shaft Lever and is positioned as seen in Figure 28.
Figure 28
19.
Reinstall the Reverse Shift Detent, Guide Bolt and Shift Detent (use a
thread lock) and you are all done. Again, refer to the Appendix for
the service manual instructions for proper torque specs.
Appendix