New to the forum. Have A 1985 S10 Blazer 4X4 2.8L automatic. Keeps pumping trans fluid out vent pipe. Been in two different transmission shops. What can cause transmission to build pressure and blow fluid out vent pipe?

 

A trans that is overheating.

 

Welcome to the forum first off. Glad you found us lol! After you lose fluid are you having to add more fluid to transmission? If so what amount approximately? My guess is the fluid is entering the transfer case from a failed seal. I can’t really recall how the vent hoses for transmission and transfer case were routed together or separate for those years of the 700R4. May want to check level on T case but be prepared to make a mess if in fact it is overfilling.
Good luck
Brad