I have a 02 A4 5 speed manual with about 118K. Recently the right front tire went flat while the snow tires were on. I was out of town and the spare was put on and run for about 120 miles I guess (my wife). The spare is the same size but a different brand/tread pattern (one of the summer tires). When I returned I put all 4 summer tires on and a bearing/transaxle/tranny noise has appeared. It definitely sounds like it is coming from the front and is a humming/whining/bearing noise that you can start to hear about 40mph and gets a little louder as the car is going faster. Makes the same noise if you push the clutch in and coast. Does not appear to be a wheel bearing as there is no change when turning or when load is transferred side to side.

I'm not 100% convinced the spare tire is to blame but I'm not sure. What could the source of the noise be? Does the B6 have a driveshaft center support bearing known to go bad? I'm really hoping it's not something major like the tranny. Any advice would be greatly appreciated.

 

If you're absolutely sure the noise is not from tread pattern/wear on the current pass front tire then I'd suspect either the pinion gear or front differential. Ordinarily I'd doubt that 120 miles with 3 winters and 1 summer would cause enough stress on the differential to cause serious damage. However, the tolerances these cars are built to seem to me to be fairly strict. Should the actual difference in size between the two types of tires be significant I would suspect damage to the differential would be fairly swift.