Why is the BMW M3 E90 E92 3 Series diff often noisy ?posted on 3 September 2015 | posted in BMW Differential and axle noise
The noise problem with the BMW M3 rear diff fitted to the E90 & E92 cars is normally caused by wear to the pinion bearings.
The bearings are ball roller type and not the old style taper type.
When this type on pinion bearing wears, aside from sounding like a squealing pig, the pinion bearing preload is altered and the pinion becomes loose. It will move (in tiny amounts) back and forth with acceleration and deceleration.
You may notice the pitch of the noise on your M3 diff alter when you do this.
It is advisable to repair your M3 diff before the bearings fail completely and damage the crownwheel ring and pinion, or even worse ruin your limited slip diff.