Just to keep everyone posted in case this comes up again, it was the diff. The pinion gears were chewed almost all the way down from what the shop is telling me. I'm not sure how it happened, but either way, I just want to get it back! I provided the shop with some Pennzoil Syncromesh, as per recommendation from Demon. From what I've read, it should be a good, conservative gear oil for what I need it for. I don't need anything super slick, just something basic that will get the job done and keep the tranny lubed. When I get the car back, I might have to take some pics just for my own curiosity and for anyone elses.
