I have a 96 burb with about 87k miles. Just got it and have noticed at red lights sometimes when the brake is released I feel a thump from the rear end. My 03 gmc reg, cab truck was doing this after a few thousand miles and the dealer said they lubed the slip yoke. I put a little grease on the part of the yoke that is exposed but it still does it sometimes. Do I need to drop the drive shaft and clean and lube the yoke or is my rear end worn? I also heard the rear brakes sticking can cause this and gm has a nickle plated yoke that helps. Anyone have this problem?