Torqueflite 904 rear seal

Fatsco knows what they are doing. I delt with them for many years. Seals do not need to be broken in. That said, when installing the seal they should always have the "lip" lubricated with the same fluid that will be sealing. Otherwise the seal can "burn" up from a dry start.
PS: When I lived in NJ, I was only about 10 miles from Fatsco.