I have a 1998 Forester. I get an annoying "droning" sound coming from the rear/back end of the car. At first I thought it was tire noise. The noise seems to get louder with increasing speed with the max around 55 mph. Around 60 mph the sound actually decreases. The shop rebalanced/rotated the tires... they thought it was possible related to the rear differential. Any thoughts or suggestions? How bad, i.e. expensive, is it if the probably is related to the rear differential? Thanks...
Stuart