My nicely built 305 h.o. and 700r4 tranny is giving me a problem, the car engine tranny are origional 84, the trans was rebuilt and has a b&m shift kit in it, no stall speed aftermarket converter. The car rows through the gears great going forward but when you put it in reverse it takes a 1000 rpm or so to back it up!! When I built this I put this car up on jacks and ran it for a good while at idle in gear as to get the fluid running through the tranny and converter, any tranny guru's got a good idea of whats causing this minor issue? Engine and trans have 70 miles on it since being built, not hard driven either.

 

My guess would be a partially plugged passage or a torn seal. Something that is causing less pressure to go to the rev clutch.