Hey Fly, it was the rear differential. It blew up on Fins and Things in Moab last weekend. Brent Brown Toyota has it, and I think it should be ready for the weekend.
ActionJackson, thank you for chiming in! I may take you up on that. I don't know if I will have time to go retrieve the Montero in Logan, but if I the dealer says he can't guarantee FJ by Friday, I may have to make the trip.
Smigette, don't be dissing the Montero

that car won the Dakar Rally (ok maybe slightly more modified than mine

).