Rear end noise...what the heck is it?

It's in my friends. When he spins his rear wheels off the ground they sound much like a X303 cam in a 5.0 idling. It's weird but that is what it sounds like...like a clunking noise...its not the brakes or anything...I haven't heard a bearing make a noise like that either...is it possible he grenaded somethin in the rear end ya think...or some causes?
 
i had a wheel bearing go out once on me in my 70 cougar, and it was a clunking sound, i know if it sounded like a b-303 cam lope, but at low speeds i guess it could have sounded similar to that, that's my best guess
 
hey we have the same sound the clunking sound an dthe loping sound also i check the greese in the stump is there any other check i can do

the clunking only happens when you get on it hard like in a bind i guess the loping starts of slow and faster when you get faster driving sounds like we had the same problem??