Differential noise between 120 to 140 kph

[omera60]

Hi All,

I'm having some noise problems with my 1990 316i Auto. When I almost depress the accelerator when the car is going between 120 to 140 kph I hear a whining/grinding noise coming from the differential. But if I press on the pedal or completely let go the noise goes away so I presume it happens in that sweet spot of load shifting. I use the BMW's own differential oil, BMW Synthetik OSP as they suggest. I replaced the pinion bearing (center bearing) and after driving for 2000km re-tightened it but the issue persists. I change the oil at regular intervals of 2 years, the car is at 62000km. When I first got the car, during the oil change I noticed some shavings but nothing major. After that, I don't recall seeing any shavings. Sideshaft bearings seem fine. Turning doesn't seem to affect the noise, only the speed and throttle input does. Any ideas what may be causing it, I greatly appreciate your inputs...

Best,
Omer

[martauto]

Sorry but did you really mean 620,000km ?

Mart.

[omera60]

Sorry but did you really mean 620,000km ?

Mart.

Hi Mart,

Sorry my keyboard must've got stuck Hopefully I will see those km's, who knows maybe a million km E30

[Contours]

A bad differential would start to whine and this would become very evident at 40 mph and would be quite deafening at 60 mph so I would think it would be unusual if its the diff. Sounds from under the body can be confusing as to their location at speed. You'd need a passenger or someone to drive the car so you can maybe pinpoint if it is the differential.

[omera60]

A bad differential would start to whine and this would become very evident at 40 mph and would be quite deafening at 60 mph so I would think it would be unusual if its the diff. Sounds from under the body can be confusing as to their location at speed. You'd need a passenger or someone to drive the car so you can maybe pinpoint if it is the differential.

Thank you for the answer. I did as you suggested and took my mechanic with me on a road test while the rear bench was removed. After some driving and listening he told me that it is indeed coming from the differential (or at least the whereabouts of it). Upon returning to the shop we raised the car and he put his endoscope camera inside the differential from the oil filling opening. What we saw was that everything inside, the gears, bearing like parts etc were in perfect condition. No metal shaving either in the oil or on the gears. We rotated the tires both together and individually to see the mechanism while the camera was inside and it seemed perfect. No issues inside. After this we decided to put a tube of MoS2 from Liqui Moly for gears. This stuff worked magic on my Z3's manual transmission where there was a shifting problem to 3rd when it was cold. I'm now testing it to see if we get any improvements from it. Otherwise I am open to ideas on what else it might be? Thanks again...

[Contours]

Is it possible that it may have been run without oil for a while. Considering that I have 340k miles on my original diff which is still quiet it would be seen as a fairly robust item. Having oil in there is the key. Hopefully you can get it sorted.

[paultv]

Do you mean the input shaft pinion bearing was replaced? The one at the front of the diff where the prop attaches?

If so, you say

" I replaced the pinion bearing (center bearing) and after driving for 2000km re-tightened it but the issue persists. I"

Setting up the pre load on the input bearing is an exacting process, if it was done by a professional diff shop and then re-tightened you will knacker the gears in the long run as the crush washer would be stuffed and the run in/out of the pinion gear would be altered.

Watch Stevies video in "Restore it" section on here..or directly on Youtube about 16 minutes in is the pre-load section:



It's for a 188 LSD but same principle applies.

Paul