1994 740I, 151K miles. Over the last year I have battled with a rear end rumble between 50 and 65MPH. Appears to get worse in the rain. Rear bearings have been replaced, drive shaft replaced 2 years ago, dog bones replaced and still in good shape. New balanced tires (17 in wheels). Jacked up the rear yesterday to see if I could find anything loose. Nothing. Don't know if this is normal or not, (I've had this car since 1999 , @65K miles, and done a lot of the maintenance on it myself.) With one wheel off the ground, car in neutral, I can rotate the wheel in the forward direction relatively easy (can spin it for about a quarter turn). If however I try to turn it backwards, it is extremely stiff. Same condition exists when I try the opposite wheel. Is this normal? Anything else I should be looking at?