I'm going to assume she means the rear diff in the rear end, since she mentioned the axle bearing too. If so, I'll say this about the differential; anything can have a minut, undetectable manufacturing defect from the start that may or may not cause a failure down the road. I really doubt the differential was damaged in the wreck, but it's not impossible. Either way, if you had it repaired by a good mechanic you will probable never have to worry about it again. By the way, welcome to the board and don't hesitate to come here when ever you have tech questions about your truck; everyone here is very helpful.