transmission problems on 1996 Chevrolet 1500 Pickup

my 1991 chevy 1500 4 wheel drive is having problems shifting into second and third the fluid looks ok and full could this be a vacume problem

Asked by for the 1996 Chevrolet 1500 Pickup
does it shift into second and third??

could be the governor and/or the gear.
could be a tps sensor or it could be internal.

the truck shifts hard into second and third at high rpms. where would the governor be located on the