The first thing I do is clean the mating edges of the transmission pump and the differential case. After scraping off the ultra-gray sealant and cleaning with a scotch pad surfacing disc I file down any high spots on the differential case mating edge. It turns out there are a handful of them. Anytime you dent a mating surface that metal is displaced making a high spot in the surrounding area. Low spots get filled with sealant. High spots mess up everything.
1st high spot removed:
2nd high spot removed:
3rd high spot removed:
4th high spot removed:
5th high spot removed:
Mating flange of differential case in good condition:
