Well, Fabrico, it appears that you were right. They found nothing, except a service bulletin that mentions the diff clutches may lock up in cars that don't turn much. I thought it was an open diff.
As it happens, the last 35 miles of our trip was on a fairly twisty road, and that was enough to fix the problem.
The service manager asked if I had changed the lube. I hadn't even checked it. She had spoken to my wife earlier, and mentioned a non-OEM color, which is about when my wife decided to wake me. The dealer is going to add some friction modifier.
Mike Halloran
Pembroke Pines, FL, USA