This does happen, I tell my customers not to tow anything for 500 miles after a gear swap. I have had 2 not listen and I had to tear them back apart. Even though it was there stupidty I still covered it, but any diff shop will tell you the samething. The heat is incrediable as they breakin and the added stress just kills the diff.
Anywho I would be in the service Dept also raising some he.....LL