BMW Blog

Anyone ever replaced a pinion bearing?

How difficult is it? (I assume it's pretty involved)

EDIT: Doing some searching I see the differential is actually pretty easy to remove from the car (hopefully this holds true for the 318ti).

Apparently the differential is fairly easy to remove from the car, but if replacing the pinion bearing requires removing the pinion gear, which it almost certainly does, then you're going to need a mechanic trained in setting up axle gears to finish the job.

Just curious, but what are the symptoms of a bad pinion bearing?

Thats what I guessed, backlash and all that crap. I plan to remove the differential and bring it in to the shop and have them replace the bearing. (Figure it'll save me some labor costs).

The symptom is a very faint whining sound from the rear center (not louder on either side left/right), it almost sounds like just some wind noise. It got louder the faster I went too. But, the mechanics put in on the lift and ran the car (in gear) and were "99% sure" it is the pinion bearing.

I just hope the bad bearing hasn't wrecked the differential gears as well.

Well if it is the bearing, I wouldn't worry much about the gears, they are hardened. It takes more than a bad bearing to hurt them.