i had this sound that no one could not tell me what the hell it was. this was when i was a kid sounded like the fly wheel that was crack.i had a 396 bbc in the gto so one day i put it to the floor till it was gone? NO.. big bang.. busted the rear end half busted some of teeth off the pinion and many off the ring and crack the case from the cover to the front seal and busted up the limit slip all to hell some of the spider teeth fell in to the ring and pinion but i did make it home going about 3 miles a hour you could get out a walk faster