Consult a Local Transmission Shop
what would transmission not to shift in to overdrive
The gears in your transmission may be sticking or worn out. This would cause your transmission to not be able to shift.
Leaky transmission lines would cause the fluid level to drop and eventually cause the transmission not to shift and go.
Sounds like a grenaded transmission
A bad transmission.
Transmission trouble
Linkage adjust
The same thing happened to my dads 96 Chevy S-10. The transmission was rusted not allowing it to shift. I would have the transmission checked out.
There could be a number of reasons why your truck will not shift properly. There could be something wrong with your clutch or transmission.
if it is automatic then this would be caused by shift down is not working in transmission
It retards / slows the timing up and makes the transmission shift hard. The engine has to be running right for the transmission to work right. It would really help to know the year. There could be other problems depending on the year.
you have to put your foot on the break pedal, to shift out of park its a safety feature