My 07 A4 with 55k miles has a strong vibration that seems to originate from the rear. It's most notable at 75-80 mph, below that speed it's fine and fades out completely above 85. I could feel it through the floorboard and seat with no shimmy through the steering wheel. Occassionally there is no vibration at speeds I would normally experience the vibration, so it is intermittent. I haven't found anything that seems to triggers or eliminate the problem. Rotated tires even swithched tires and rims with a brand new set that were load forced balanced... still the same issue. Dealer changed axle oil and that helped lessen the vibration by about 60% but not a full cure. I can't find anything in the suspension that appears out of order. I do most of my traveling on interstate highways and drive in the speed range where this issue occures. It very frustrating, any suggestions what this can be?

 

have you put on any aftermarket wheels? some aftermarket wheels use an insert that is out in between the wheel and the axle tip that you put the wheel on. be sure to remove that insert when you use the OEM wheels. explain the history of the wheels/tires. you may also have a puncture in a tire. a screw or whatnot into the tire will throw off the balance at highways speeds.

 

It's very possible that something inside the rear differential is damaged. What leads me to believe this, is your statement about how the fluid change helped reduce some of the vibrations. The only other thing I can think of is possibly having a brake rotor that is warped. However if it was the rotor then changing the fluid wouldnt have done anything to reduce the vibrations. And since it is occuring between a specific mph I feel even more strongly about it being an internal issue with the differential.

I would take it in to the service department & explain the symptoms to a technician. You might get lucky & it be a simple adjustment or part of some sort. Whatever the issue I would have it checked out before additional damage occurs & the repair cost skyrocket...

 

Probably a failing axle. It could vibrate worse as time goes on. I had a front axle start that way and progressively got worse. I only say axle after tires and rims are ruled out. A rotor would only vibrate under braking.

 

I noticed the vibration is almost eliminated when the outside temp is warmer. It's starting to warm up and we reached the 70's for the first time in quite awhile and no vibration not matter what speed. This may sound weird but it was in the late fall, early winter when this problem developed when the cold started to set in. So it seems like it may be temperature related.