99 olds bravada

got a 99 bravada today was told it don't go into rev every time. tranny shop said sensor, that possible? have a 91 s-10 for years dont know any thing about these. it sat for 2 yrs and don't know if was that way befor it parked or not . Any advice i have been wrenching on cars for decades but the new ones !!! :confused:

got a 99 bravada today was told it don't go into rev every time. tranny shop said sensor, that possible? have a 91 s-10 for years dont know any thing about these. it sat for 2 yrs and don't know if was that way befor it parked or not . Any advice i have been wrenching on cars for decades but the new ones !!! :confused:

Possiable shift linkage or low on fluid.
But no reverse usually = internal problems.

Any transmission codes?
How is fluid and filter?
Fluid level?