Hey guys, i have 2000 expedition, was backing out of driveway, place car in drive and heard a loud clunk in the rear somewhere. Since then, i will occasionally hear a wop-wop-wop-wop, almost like a flat tire sound, or something rubbing. Sometimes it is more metalic sounding. i have been all over the rear end of my truck, removed the wheels and brakes, inspected my coils, shocks, control arms, etc. I don't see any cracks broken bolts, ....nothing. It drives fine, it just makes a lot of noise at very random times, there is no consistency as to when or what conditions it happens with. There may be a slight leak of some sort where the rear axle/housing thing meets the tire. ALso, i believe i have narrowed the sound down to the right rear. Any ideas?