Ouch, had the same thing happen to mine. Had them replaced, and 6 months latter them bitchs went out again. Just buy a used rear end, same price, better outcome.
Fuck bro, and there was no way this guy could have figured this out without making you buy new spider gears?
Sounds like both needed replaced anyway, sorry to hear that tho
The bastards also put over 80 miles on my truck. I guess they had a little too much fun test driving it.