Problems with an AOD
 

Hi everybody,
I just bought a '90 4x4 150. I was told the gasket-seal between the tran and transfer case was leaking and needed replacing. But was assured the transmission was fine. Wrong! I filled the transmission up with fluid and tried it out. While in park and reverse the truck acts like it's locked up in two gears and motor won't tach over 1300 rpm. Drive gears seem to work ok and motor will open up. Oh and it also moves in nuteral. I'm hopeful someone has a clue about what's going on with this thing. Thanks for your help.