Tom in Austin

Shims are item number 6 in the image. Someone posted a while ago saying they were advised to first loosen and then retighten all the torque tube fasteners at either end to relieve the relative positions of the engine, tube and transmission. Then raise the transmission, measure the gaps below the mounts, and add any shims needed.

I'm interested in this subject because so many 928 torque tubes have been removed and reinstalled over the years (including mine by the PO's dubious shop). If aligning through shims and/or relieving the entire drivetrain is necessary (they did put it the WSM after all), then how many of our cars are running around unaligned?

the flyin' scotsman

any update Jeff?

aligning the TT.....anyone asked Constantine?

jeff spahn

I am going to do this either Friday or Saturday. I didn't see any shims when I took the bolts out. That doesn't mean it won't need some now though I guess. I'll loosed the tt bolts at the bell housing and the tanny mounts and then tighten all at once now that the engine is in place.

the flyin' scotsman

Look forward to reading your findings.....the 87 Im working on goes home next week and has identical problem.

Aloysius

I'm not sure how to check this but the trans mounts are 2 pieces of metal with rubber bonded between them. I've seen old ones where the rubber cracks and you can basically pull the 2 pieces of metal apart as the rubber crumbles between them. I don't know if this is a good idea but you might try jacking up the transmission very slightly and inspecting the mounts for cracks - heck maybe you can see them without doing this but my guess is the weight of the trans will make hard to see - unweight the trans and I think they would show up. Of course you'll probably make some new ones if you lift it too much . . . ideas anyone?

My thinking is the trans is moving on the mounts as all the forces from the drive axles act on the transmission and might create enough disturbance to cause a speed related vibration. reaching . . . just thinking out loud. How old are the trans mounts? Original? I'm also thinking that sliding the trans back on the mounts like you mentioned could tear the rubber, especially if the trans unit is resting on them as you slide it back.

killav

Jeff,

If you can get your hands on an IR (temp) gun, I would shoot the back rotors where the emergency pads reside and see how hot things are after your 10 min drive. If your e-brake is super tight now, it is possible that the pads are being applied some causing then to heat up and maybe sticking or grabbing or something once they get to a certain temperature. It's a long shot I know but worth checking.

Bill Ball

I kinda wish I had left the original mounts in. They only had 200K miles on them. They were somewhat collapsed, but the tranny still sat properly above the crossmember and I had no vibration. Reminds me that I had a similar experience when I replaced the original Boge red shocks at 110K miles with something else and ended up with one of the worst handling 928s around. Still struggling with that.

jeff spahn

I am not sure how old the trans mounts are. A new transmission was put in by Greg Brown at about 70,000 miles or so. I have 125,000 on it now. If I were to ASSume, Greg would have replaced the mounts because he is the stickler for detail for working on our cars. Then again, I didn't see trans mounts listed specifically on the repair bill so . . ..

Just for ****s and giggles I could replace the mounts anyway and see if this removes the vibration. Doesn't appear to be that bad a job.

I'll try to check the brake this weekend and the spacing on the trans like Bill Ball's suggestion and then report back.

If after fixing both of those it doesn't stop (didn't happen yesterday or today), I replace the trans mounts.

jeff spahn

Well I looked at the transmounts this weekend. They are in really good shape. Spacing on each side of the transmission is just fine. And. . . there is no more vibration. I loosened the brake cable at the handle and we will see if that was it.

For now, I'll have to consider this closed.

Black Sea RD

Sounds like it was the emergency brakes getting hot and then juddering when you kept driving with them somewhat engaged. Did you happen to smell the telltale odor of hot brakes when you were checking your car over after running it?

If you check your parking brakes in the future you wil probably find some worn down or very shiny parking brake pads.

Of course I jump in now and say this...

jbrob007

Apparently quite a few of our cars do this Mine vibrates up through the floor / seat (not the steering wheel) @ a range of 80 to 85 mph... Ground force & high spin balanced all four wheels - no change. I'm no expert by any means, but this frustrates the hell outta me as well. If its something as simple as adjusting the parking brake... well, I'd be a VERY happy camper

jeff spahn

You know ,that's the funny thing. No hot brake smell at all. It really flummoxes me that I couldn't figure this out. I looked at the brake cable routing this weekend when I was under the car looking at the trans mounts. They look like they are routed exactly like they were when I took the cable down to move the trans back. It made me wonder why the heck they would be rubbing.

Anyway, I'll try it this week and see what I get. So far no vibration.

Black Sea RD

Could you have tigthened the nut too much when you re-installed the cable back on the emergency brake handle? I remember usually having to re-adjust it a bit after doing TT and trans R&Rs. Sometimes I tightened it too much which did not allow the e-brake handle to travel as it should.

Hopefully you found the root cause of the vibrations.

Cheers,

Bill Ball

Weird. My parking brake operates just as it should. Hope your vibration is truly gone. Like jbrob007, mine has persisted despite checking all the usual suspects.

jbrob007

Was anyone able to come up with a verdict??