Welcome Jon

1991 exccel
I changed the transmission fluid chnaged filter now tranny slips and shakes.
Ran fine before. At start up from a light or stop is main problem. If I
manual trrought gears, not as bad.
Have been told I should have left the old muck in there. Got a bottle of
Lucas Transmission fix and will try that for now. Anyone have a used
Transmission ?

hyundaitech

What transmission fluid did you use?

Are you sure it's full? You should be checking the fluid level with the
vehicle running, warm, in neutral.