Hey i'm building a 91 ext cab truck out of a few trucks. It was leaking oil at the back of the motor when i got it so i put an old valve cover gasket i had in it, and it seemed to stop. Also could use a half moon gasket.

Today when i was switching the trannys there was a puddle of oil in the tranny i took out of it. It was also missing the 2 bolts at the top from the tranny to the motor. Is this probably just the valve cover gaskets that were leaking or could it have been the rear main? Is there a way to tell if it was the rear main seal?

Also the tranny i took out of another truck to put in this one,i had it standing straight up and down. I noticed there is gear oil leaking from around the tcase shifter. Is this normal because its standing straight up and down or is there something gone thats making it leak?