I'd use the same fluid if I were you. Ive watched and caused the demise of a few transmissions after fluid changes. Older ones of course. One day a mentor told me to save the old fluid and just change a filter in a th350 I had slipping and I believe that thing is still on the road. Something about the detergents or something in new atf will destroy seals and soft parts. I'm sure somebody can explain better, as my limited expertise ends after the flywheel.