how do i know if my transmission is going out on 1991 Acura Integra

my car is not able to go over 30 miles per hour but all the geers go in good

Asked by for the 1991 Acura Integra
It could be for different reasons, like a clogged catalytic converter, restricted air intake, etc...
Better to take it to a repair shop and ask for a diagnostic. They will be able to pinpoint the cause, this way you don't guess and replace unnecessary parts.