Does anybody have experiences with a whining noise coming from the rear differential of a Z3? You only hear it with the top closed, around 50 mph, then it disappears completely at higher speeds and comes back around 75/80 mph. Mileage of the car is not even 30kmls. The whining noise was not always there. At some point in time it started and gradually increased. A BMW service Rep. claimed this is normal, can not be repaired and may happen again with a brandnew differential. Any thoughts or experiences? :dunno: THANKS!!!