rear differential trouble
 

I have a 01 a4 Quattro (113,000 miles)that is making a humming noise from the rear differential (loudest at 50 mph). Diagnostics so far: I put the car on a lift a spunthe back wheels, no noise was coming from the wheel bearings. I then spun the wheels as fast as I could and listened to the rear diff where I could hear a low clunking noise. I checked the fluid it was clean and only an ounce or two low. I am assuming that the bearings are going bad.

Questions: What commonly goes wrong in the rear diff? Where can I buy the bearings? What other parts should be replaced at the same time? What is the estimated cost of having this job done at a shop?

Thanks in advance…

RE: rear differential trouble
 

Never heard of one going bad. I'd drain the oil and replace it with fresh synthetic anyway.

Sure it isn't your fuel pump making noise?

RE: rear differential trouble
 

Sure it isn't your fuel pump making noise? >

I could hear the noise with the car off spinning the wheels on a lift. The sound was coming from the diff 99% sure.

RE: rear differential trouble
 

bearing noise by what you say ( it will only be audible under load ) so jacking it upevades the problem, im going bearing