I have a 1991 240 DL, 151,000 mi, with rear end noise. At least that's where it sounds like it's coming from. It's a whiring noise that follows the speed of the car. The faster you go, the more high pitched it is, eventually disappearing around 30-40 mph. First off nobody seems to want to work on Volvo differentials. Talking to one place that said reluctantly, they would look at it and also said it could run as much as $2 K to fix. Is there any other possible source of this noise? And if it is the differential, is it really that expensive? If this is a differential problem, is it best to let a dealer do it?

If anybody has any input on this, please respond. Thank you!