gijsbert

My first post on this forum, but I have been reading along for quite some time.

I purchased a 928 S4 automatic 1991 from Japan. Very low mileage car (41000 km) and in very nice condition inside and out.

However there was a constant whine coming from somewhere under the car. It became louder with more rev's. With all the very usefull write ups on the forum I checked the flexplate. It had around 3 mm load on it. The thrust bearing play (measured with dial indicator) repeatedly measured 0.22 mm. I was very pleased this was within factory spec. I further prepared to rebuilt the TT en TC bearings. But after the flexplate release the whine was gone.

-Does anybody know if the whine will return shortly and the bearings are allreade toast or there is a possibility that the bearings are still OK?

-Are the troubles of TT and TC bearings mileage dependent; as my car has only traveled 41000 km, it seems a bit early for these problems to occur?

Leon Speed

What did you do to prepare for rebuilding TT/TC? If not too much then I'd say if it's gone, drive it until it returns (if it returns).

Bill Ball

Never heard anything like this from just 3mm of preload, which is a quite common "equilibrium" state - not good but common and not bad enough to cause excessive TB wear. It would be hard to say what as responsible for the whine - TT, TC, ring and pinion, some other internal tranny bearing. If you have no other indication (vibration, constant noise) on such a low mile vehicle, there no good way to determine what to do.

I've had a whine from somewhere in the drivetrain, but only in park or neutral (disappears in gear), for over 4 years and 50K miles. It has never changed or been associated with any other issues, so until it declares itself more clearly, I've just left it alone. I'm still on the original TT and TC bearings. There's no vibration, growling noise or whine that has changed character.

In your case, since the whine went away upon relieving the flexplate preload, I'd put on either Constantine's superclamp or PorKen's PKlamp, which should stop the return of preload. Glad to see your crank endplay is good, only slightly more than mine.

Mongo

I have lots of growling and a strange noise in mine at idle regardless of gear. I posted about it a while back and it was diagnosed as aging carrier bearings in the torque converter. Releasing the flexplate pinch collar did not make the problem go away.

gijsbert

It sounded exactly like this one I found on youtube (although not quite as loud)

http://www.youtube.com/watch?v=x0_hxChnwss

the whine did not differ in N, D, R, P. It was there from idle and became louder with increasing RPM (just like the clip above)

Black Sea RD

What we've noticed is that drive shaft tension due to flex plate load will cause the premature wearing of the torque tube and torque converter bearings. These bearings are not designed for this sort of axial loading under operation.

Releasing the tension will alleviate the bearing noise but the bearings are on their way out.

HTH,

Imo000

Drive it until the noise is constant, then replace the TT and TC bearings.

Mrmerlin

this is a sometimes common noise with a preloaded flex plate.
Glad you checked the tension,
make sure to also check the rear pinch bolt at the transaxle or you may wind up with the same noise.
Really check the rear bolt first then tighten the front bolt after the rear bolt has been tightened, 66ft/lb with blue loctite on the bolt

Tails

Good to hear the crankshaft thrust bearing is within specifications and that the front flexplate has been released.

+1 on Bill's comments regarding front flexplate migration and Thrust Bearing end play.

It is advisable to check your forward flexplate migration, regularly, or at least once per year at the yearly service, but it sounds like you will get an indication if it migrates by the return of the whine.

If you put some white paint in the spline and clamp, you can check for migration through the small plastic insert at the bottom of the bell housing. I made a small light that I can insert into the bell housing to light up the area where the paint has been applied.

The torque converter bearings are not thrust bearings. You probably don't know if the flexplate has ever been released whilst car was operated in Japan? In my experience the Japanese are very good at making new equipment, but they are no as good in the repair and maintenance field, as they mainly undertake repairs by replacement of the part, especially under their government motor vehicle inspection regime or registration.

This could indicate that the flexplate may never have been released in the 41km, so the Torque Converter bearings could have been under axial load for a considerable period.

I also agree with Bill to fit a Constantine Super Clamp when the TT is removed for overhaul or as an interim step at least fit a PKlamp to stop the migration.

I would suggest that if no whine then no continuous thrust force on the roller bearings within the drive train, so continue to drive the car until the whine returns, whilst keep checking the flexplate migration.

When the whine starts to return with no flexplate pre-load then this would be a good indication the the roller bearing are on the way-out.

Tails 1990 928S4 Auto

borland

One way to isolate the bearing noise from the engine noise, is to kill the ignition switch with the tachometer showing about 1,500 RPM. That kills the exhaust noises, so you should be able to hear the bearings better as the engine rotates to a complete stop.

Most over estimate the complexity of replacing the torque converter and torque tube bearings and end up tolerating driveline bearing noises. But I recommend replacing them every 75K miles, because the car is a much nicer ride with newer torque converter and torque tube bearings installed. Besides, you won't need to check the pinch clamp as often.

Imo000

Over estimate? I disagree. It is not a simple thing to change.

gijsbert

I can agree upon the remark about Japanese maintenance. As the original wax coat under the car is completely intact I can confirm the Flexplate has never been checked before. Probably most cars have not been checked during the first years when they were driven from new, as the problem was not yet recognised.

I will continue to drive the car until the whine re-appears.

But I am dreadfull for the amount of work involved in a bearing replacement job. From the write-ups I understand most people put the car on axle stands (and manage without a lift). I do enjoy working on my cars, but the complexity of the rear suspension having to come off and difficult acces worry me a bit. How many hours would this job take a moderately experienced DIY mechanic without a lift?

Bill Ball

Working alone - figure easily a full weekend. Somewhat nasty job on your back pulling the exhaust and then the entire rear suspension, then extracting the TT and tranny. You would need a press to do the TC bearings.

I've done this without removing the rear stuff by sliding the tranny back and tilting the front of the TT down for removal, but that is unconventional and requires some creativity at a few points. Here's account of what we did...
https://rennlist.com/forums/928-foru...tos-added.html