I got a tow the other night because my truck was making funny noises.
The local Toyota dealership diagnosed a broken diff and wanted $2000+tax to replace it.
I just got off the phone with the independent Toyota mechanic and he can't find anything wrong with the diff. No noises, no broken parts, etc etc. The bearings are fine and he's road tested it with success. In fact, he can't find anything wrong with anything...
Since it's at the shop I'm going to have all the oils changed (motor, both diffs, and transfer case) and have the drive train lubricated. I'll be back on the road in no time, and for a small fraction of the expected cost.
The moral of the story? Always get a second opinion. And check your lug nuts once in a while, kids.