got a 91 automatic transmission in it and it idles fine and nothing overheating.
i noticed it drives normally when i first turn it on but even then it has trouble shifting up and im usually stuck going between 20-30 mph if i try to go higher it jus revs like its in neutral. then once i feel its slipped the only way to get it to engage again is to turn the engine off and start it up again then the tranny works. did some searching and came up with either the auto tranny filter is clogged, torque converter needs to replaced, or entire tranny needs to be rebuilt. anyone else had this problem before?

side question: how much to swap for a 5 spd?