HELP!! GM Auto TRANS shift problem

80s GM 3 speed auto.. wont shift out of first gear till I hit 35 MPH (60 kph)
Any ideas??

 

Do you have the vacuum line to the modulator valve hooked up? could be a problem with the governor also.

 

What trans is it?

 

Trimatic, the vac hose is on to the modulator also
Q? If the modulator was stuck would that do it?

 

the modulator ( little bell looking thing at the back of the trans on the pass side) could be bad , stuck or hose bad. a new one isnt much and it has a set screw that will help set your shift points.