Possible spring shot out of gov. this is very common and easy to fix, also may be lose vb bolts or leaking accum. or lose bolts on housing. these are just a few suggestions.
How 'bout a little more info. such as what trans, how long has it been like this, just happened, just got it, always been like this, any mods, how many miles and so on.
Before this happened the trans would only shift at high rpm.
Would not go into overdrive until 80 to 85 mph.
Pull out of the garage and it would not shift out of 1st.
I bought the car in march 2002 had the motor rebuilt with
forged JE's 218/218 comp TA49 with big exhaust housing
3 inch dp cnc iron heads campion ported stock intake.
Had not purchased injectors yet. As for the trans I have no info.
may wanna take a close look at the tv cable., Mine streatched (original) and allowed a failsafe spring and rod pull out of the vb dropping a ball and pushing tv pressures to max. My car would not shift out of second.