Help locating bearing whine

[camplo]

I have had my e28 for a few months only, but the previous owner did a great job restoring the car. The car has a loud whine which I thought was from the input shaft bearing on the diff, but I am starting to second guess it. When the car is in gear and accelerating or decelerating I can hear the whine. When the car is moving but not in gear, there is no whine. Could this be the transmission or center support bearing? Or was I correct to suspect the diff?

[tn535i]

It can be difficult to tell for sure but anything that changes with acceleration/deceleration loads is clearly part of the driveline. If it does not change with the gear you select then you have eliminated the transmission input bearing but that's about all. Sometimes the frequency or pitch gives you a clue. Higher is usually driveline, lower is axles, wheels. But a sticky u-joint might not be that noticed until your speed is way up than felt as a stronger vibration. I've been wrong as many times as I've been right guessing what was bad on various cars.

[camplo]

It starts as soon as 10-15mph and is louder than my exhaust leak. The faster I go, to louder it gets, take it out of gear and its quiete. I guess I'm having a hard time because its only noticeable when in gear. Doesn't the drive train, specifically driveshaft, all spin even if I'm not in gear?

[tn535i]

Output shaft of trans, driveshaft, differential, axles, wheel bearings all spin together at their relative speeds to vehicle speed, never changing except only slightly for L and R axles when turning.

Wheel bearings typically change as they load and unload with turning but all the rest above changes with engine load or engine brake. Regular brakes applied out of gear may impact wheel bearing noises but not driveline noises.

[Mike W.]

Yes it all spins at a progressively increasing rate, excepting parts of the transmission, but the load on it can make a big difference. My experience is diffs growl but transmissions have a higher pitched noise, but not necessarily whine. From your description it sounds like the tranny, but those noises are awfully difficult to diagnose. Experience helps, but is no sure thing. I would not guess driveshaft, but that's not an absolute statement.

[tn535i]

never changing except only slightly for L and R axles when turning.

That should have said never changing relative to road speed.... but I think Mike made that clear. The transmission might be a place to start if you have never changed the fluid. As in another post most would recommend Redline fluid, MTL or Maybe MT-90 if you live in a hotter climate. Another thing that can really transfer noises is bad bushings, rear sub frame or transmission mounts if they are bad. All of this stuff is noisy to a degree but usually isolated OK. The lowest cost item would be a center support bearing on the D/S but generally when something in the D/S has gone bad you feel a shake/wobble in the seat of your pants start at low speed then go away,then progress to a higher speed vibration. I've never had a whine from a bad CSB but might be possible and it will move some with load. But the description sounds more like transmission or differential. Both could have fluid exchanged to see if anything changes. It may not fix it but might make it different. Do one at a time.

[camplo]

Thanks everyone. I did some searching and wanted to use amsoil 75w90 for the transmission but wasnt available at the closest parts store. Will look again at other places. The previous owner changed the diff before selling me the car since it was shot. He says the noise is from the diff and to use MT90 or replaces with a working unit. I'm still skeptical since the whole on/off load thing. Will do the transmission fluid first and go from there.

[Aldo525]

Hello, I revive this thread. Maybe somebody here can guide me:

My car has a noise, a whining noise that comes from the rear area and which, according to my experience with old BMWs, is typical. My father's e30s had it (all with over 100K) and my e28s have it. We were never able to figure out what the sound was. As a rule, I can mention that it is not the gearbox (new), it is not the central support of the driveshaft (new), in the e30 it continued to make noise even after changing the front and rear wheel bearings and I can only think of something in the differential, They were never rebuilt but always with new oil (SAE 80w90) and no LSD.

The noise is felt when moving forward, no matter the speed of the car or the engine or the gears and it does not change when you touch the brakes a little (not even with the hand brake), so I suspect that it is some issue with the differential.

Has anyone diagnosed it and solved it?

87' e28 euro 525i

[gadget73]

I don't know BMW's but other vehicles I've had with a speed-dependant and somewhat load-dependant whine were often pinion bearing problems. usually not enough preload specifically but it depends how the rear goes together. Things with crush collars to set the preload are prone to losing preload over time, ones with shims not so much.

There is probably a spec in the book that uses a beam-style torque wrench to check rolling resistance on the diff to verify proper preload. Its usually some small number of inch-pounds or whatever that translates to in metric. Newton-centimeters? Or maybe its just a very small number of newton-meters. Either way, worth a check, maybe it will tell you something. Make sure the brakes aren't dragging or it throws this off completely.


If the diff has been apart and any parts in there changed, all bets are off. Moving the gears relative to one another or any other incorrect setup can cause a range of noises.

[Aldo525]

I don't know BMW's but other vehicles I've had with a speed-dependant and somewhat load-dependant whine were often pinion bearing problems. usually not enough preload specifically but it depends how the rear goes together. Things with crush collars to set the preload are prone to losing preload over time, ones with shims not so much.

There is probably a spec in the book that uses a beam-style torque wrench to check rolling resistance on the diff to verify proper preload. Its usually some small number of inch-pounds or whatever that translates to in metric. Newton-centimeters? Or maybe its just a very small number of newton-meters. Either way, worth a check, maybe it will tell you something. Make sure the brakes aren't dragging or it throws this off completely.


If the diff has been apart and any parts in there changed, all bets are off. Moving the gears relative to one another or any other incorrect setup can cause a range of noises.

Hi, thanks for your comments...There is a pinion preload of just 2 Nm....is a little amount I must to check. Trying to figured out the noise problem I found this youtube video about a guy disassembling an e34 diff explaining all the process. Seems not too difficult the internal bearings change. I believe this will be my next challenge repairing the e28.

https://www.youtube.com/watch?v=UkytBJk ... MplusResto

[gadget73]

Nice that you can just pull the whole thing out of the car and do it on the bench. Mine are all solid rear axle cars, not impossible to pull from the car but a lot of work. You end up doing all of the work under the car which is not a lot of fun.

looks like a crush sleeve like my Fords use. The usual stated fix for that is a new one, but when I did the pinion bearing seal on one I found in the factory service manual that it was OK to tighten the nut down more until it was in spec. The instructions were to check the rolling torque before touching anything and note the value. Mine was 0 in-lb, and its supposed to be 8-14 in-lb (2 Nm is 17 in-lb, so about 1.5 Nm).

When putting it back together with the new seal, it says if the initial value is below spec, tighten the nut until its in spec. If its above spec, put it back where you found it. I only had a slight whine, but when I made the nut about 1/4 turn tighter to get the preload in spec it was perfectly quiet.

[Aldo525]

It would be great if the problem is just a bit of pinion adjustment. As I mentioned before, we always heard it on the e30's and I wasn't surprised to hear it on the e28, but now at least I can check the preload and see what happens.

Thanks for the feedback.

[Mike W.]

I can't believe anyone including myself hasn't mentioned it, but there's an excellent writeup on rebuilding diffs near the top of this page. In depth and lots of pictures.

https://www.mye28.com/viewtopic.php?f=3&t=142750

[Aldo525]

I can't believe anyone including myself hasn't mentioned it, but there's an excellent writeup on rebuilding diffs near the top of this page. In depth and lots of pictures.

https://www.mye28.com/viewtopic.php?f=3&t=142750

Excellent!!!.....very useful info. Thanks Mike!!