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My MY91 S4 is now on 80,000 miles. The only niggling problem I have is a noise like a low pitched rattle at idle, more obvious when under load at very low speed (pulling onto driveway, turning into side road say). At higher speeds I don't hear anything, and there's no vibration at any speed. For anyone who knows London taxis that's the best description I can give — a kind of friendly diesel rattle! It changes in line with engine revs.
Poking around in engine bay with stethoscope reassures me it's not an engine related noise. Today I took off rear undertray and had a listen around the front bell housing, engine running in Park. It's definitely louder/detectable at the rear torque tube end of that housing. There are no odd noises listening to torque convertor at rear end.
Could this be anything to do with torque tube bearings? I've read other threads on this where people talk about rattling marble sounds, and vibrations at higher speeds. I don't experience those symptoms.
Is 80,000 miles consistent with worn TT bearings? Changing the tube seems a big job — if I don't try to rebuild the existing tube but replace with a good one, do I still need to drop rear suspension and transmission? Are there other tests I can do to check the TT bearings?
Thanks a lot!
Last edited by StratfordShark; 05-12-2018 at 08:08 PM.
I'd have a look at the Rear Flex Plate rivets, known issue, the fix is to drill them out and use bolts, IIRC there was even a service bullition about the problem.
Sounds like a Rattle, right?
The TT, flex plate and Torque Converter bearing can all be done w/o removing the Trans or engine.
I'd have a look at the Rear Flex Plate rivets, known issue, the fix is to drill them out and use bolts, IIRC there was even a service bullition about the problem.
Sounds like a Rattle, right?
The TT, flex plate and Torque Converter bearing can all be done w/o removing the Trans or engine.
Dave K
Thanks Dave - I've since seen a write-up where just exhaust and rear suspension dropped which doesn't seem too bad. I need to examine the rear flex plate, but I have a MY91 and thought the rivets were only used in early S4s? Yes it's a rattle but not a metallic or tinny one that others have described with failed TT bearings. I'm happy to change the tube, but would be good to know for certain whether that's going to be the fix!
Yes the exhaust does need to be removed, however the rear suspension does not need to be touched, just the trans unbolted from it (two 19mm bolts) and trans pushed back a bit, up front the lower bell removed and Flex plate disconnected.
The upper may have already been notched to pass the drive shaft through, the last one we did a at a tech session was, we dropped the TT and serviced it and the converted bearings in a day, had all parts on hand and a shop press.
EDIT: mind the Trans reservoir when moving the trans around that you don't stress it
Good luck,
Yes the exhaust does need to be removed, however the rear suspension does not need to be touched, just the trans unbolted from it (two 19mm bolts) and trans pushed back a bit, up front the lower bell removed and Flex plate disconnected.
The upper may have already been notched to pass the drive shaft through, the last one we did a at a tech session was, we dropped the TT and serviced it and the converted bearings in a day, had all parts on hand and a shop press.
EDIT: mind the Trans reservoir when moving the trans around that you don't stress it
Good luck,
Dave
Wow that sounds miraculous! Why do others choose to lower rear suspension and drop tranny with the tube? This sounds so simple comparatively. Is the tranny light enough to move back with a shove once the transmission mount bolts are removed? Thanks for tip on the reservoir — I think I might drain the tranny and remove reservoir if it looks vulnerable.
I’ve just found and studied this great account by Bill Ball, involving bellhousing removal but otherwise leaving rear suspension and tranny untouched as you said, other than removing tranny mount to crossmember bolts. Doesn’t look too bad at all:
Yes Bill has a great write up on this, and I've done it that way too however before you remove the upper bell and you need to look at why it as to be done, there is a small piece of aluminum (part of the upper bell, not present on a manual) that blocks the drive shaft from coming out.
That is why Bill removes the upper and turns it around to get it out, many upper bells no longer have that piece of casting, as it was simply cut out to simplify driveshaft/TT removal
I’m looking forward to checking this. I suppose it would be obvious that the upper cover’s been notched with the lower bell cover removed? If that casting has been left out then another hat tip to those far sighted engineers at Zuffenhausen.
Will make plans for this job once I’ve confirmed TT bearings are worn. Had a great 25 mile drive today in sunshine, and she was running so sweetly at speed. Yes I could detect that rattle sound at idle when outside the car - in certain spots anyway - but once off very low revs I’m not hearing or feeling anything suspicious at all. I’ll pick a time when it sounds obvious and post a recording to see what people think.
Your symptoms do sound like the rivets at the rear flex plate as DaveK9 suggested. The rivets get loose and allow the two steel plates which make up the rear flex plate to vibrate causing this rattling sound. The sound usually goes away when you load the rear flex plate when driving.
Noisy TT bearings usually growl at low speeds and change their pitch as the RPMs increase then get drowned out by other noises of the 928 under speed unless they are very bad.
If the drive shaft slipped in the front flex plate clamp and loaded up the drive line, then your torque converter housing bearings will also become noisy. But they will act the same as noisy TT bearings and usually not rattle as you described.
I just found this thread about the rivets, which includes photo of a 91 flexplate with rivets! Has image of the TSB too, which I couldn’t find when I looked through my TSB file yesterday:
I've never seen torque plate rivet problems in a car as late as 1991....I thought they had solved that problem by then.
Originally Posted by StratfordShark
I just found this thread about the rivets,which includes photo of a 91 flexplate with rivets! Has image of the TSB too, which I couldn’t find when I looked through my TSB file yesterday:
I just found this thread about the rivets, which includes photo of a 91 flexplate with rivets! Has image of the TSB too, which I couldn’t find when I looked through my TSB file yesterday:
WYIT you can also take care of the torque converter bearings, primary pump seal, do a transmission and rear end fluid service, check the health of your CV joints and rubber boots, transmission mounts and rubber vacuum hose to the transmission vacuum modulator to start.
Good luck with it and keep us informed as to what you find.
Before I owned my 91 S4 the torque converter bolts had backed out and I'm sure made lots of noise. I replaced the bearings in mine with Constantine's along with the TC housing bearings and GB's driveshaft. The rivets on my rear flex plate were fine even though the were beaten a bit by the bolts that had backed out. I drilled and re-tapped with larger bolts because the threads were beyond repair on the TC. I dropped all of the rear to replace transmission front pump and seal due to them leaking. I don't know what's up with the site but trying to upload pics is terrible.
WYIT you can also take care of the torque converter bearings, primary pump seal, do a transmission and rear end fluid service, check the health of your CV joints and rubber boots, transmission mounts and rubber vacuum hose to the transmission vacuum modulator to start.
Good luck with it and keep us informed as to what you find.
Thanks Constantine. At least I can tick off couple of items on your helpful list — changed tranny mounts last year, and have just replaced boots on the drive shafts! I did last trans fluid service about 15,000 miles ago but will need to drain and replace the fluid whatever I suppose.
05-12-2018, 01:17 PM
Torque tube bearings worn?
