Any one in the I-495/Rte9/I-90 area of Massachusetts know of a reputable Audi shop to fix a Rear Differential Bearing issue with an '00 A6 4.2 Q??? Car whines when you start rolling & progressively gets louder. Any assistance & recommendaions would be greatly appreciated. thx

as they are open differentials that then use the ABS sensors and brakes in reverse to slow a spinning wheel, faking out the Torsen mechanical center diff into sending power to wheels with actual grip.

Most often a failure is the result of running staggered wheels and tires or the car having been towed with front or rear wheels on the ground.

If anything, I would suspect the Torsen diff of being shot, but that is located towards the front of the car near the tranny and I've only ever heard of a handful that have broken - usually due to factors stated above.