Differential whine: what's the exact cause ??
 

What exactly is the typical cause of differential whine?
Is it caused by worn bearings holding the axle shafts, or by play between pinion gears? I wonder if adding some friction additive like MOS2 could help, but if the whine comes from the -sealed- bearings, that would be pointless.

Thanks.

See post #15 in thread below.

http://www.peachparts.com/shopforum/diesel-discussion/139588-1987-300d-rear-noise.html?highlight=whinepost

Whine from a differential can be caused by different problems..

IF the car has a whine early in its life like the 1981-85 380SL's had or the 1990-92 190E 2.6's, then improper gear lash or "improper cutting of ring & pinion" is most likely the problem.

If the car is over 5 years old and the diff starts whining then a bearing failure is the most likely cause.