my buddy's truck, is making a clunking noise in the rear end, the truck has 48000 on it, I am wondering if any one else has had this problem, and, or what it could be he is checking to see if he has the extended warranty on it.

the sound happens once and a while when he turns corners, or when he shakes the truck back and forth. he found the noise checking to see if his tires were on good. the sound is coming from the middle of the axle. some help would be greatly appreciated

thanx guys