I am assuming you have an automatic transmission. Check your Transmission Fluid to ensure it is at the proper level. Next check the fluids color. It should be pretty clear and red. If it is starting to turn brown or is cloudy you need to change the fluid. Make certain you are using the correct fluid for your trans. The guys at the auto part store can show you the right stuff. If none of that is the problem you are going to need to have a trans shop figure out if you have a valve problem or something more serious. Good luck.
Broken spring in the valve body per Kennedy Transmission. $180 parts and labor which includes fluid and new filter. check the tps sensor...
It could be a number of things going wrong. Try dropping the transmission pan and changing the transmission oil filter and transmission fluid.
have you checked the oil level in the transmission ? I'm betting the answer is no
no oil in trans
THIS IS A COMMON PROBLEM ON THE GM TRANS WHICH IS A BROKEN 1-2 ACCUMULATOR SPRING
When was the last time you changed your transmission fluid? As the fluid gets older, transmissions start to shift harder, and you notice the shifts from gear to gear a lot more. It could also mean that your transmission needs repair.
pulse generator is bad
I recently had this very problem with my 1996 Buick Century and it was in need of a new transmission and would have cost $1100-$1500 to fix, so I went and bought a Toyota Corolla.
This is called limp mode for that 604 transmission, it means something is wrong internally with the transmission and it needs to go to the repair shop for further diagnosis.
if it is not going into gear when it is started, if it is a standard transmission then it could be that your clutch is not engaging or that your gears are stripped in the caseing of the transmission, if it is an automatic then your torque converter could be bad or there is something wrong with the shift linkage
You probley installed the filter wrong. Remove the transmission pan and check the filter.
You probably have a slipping clutch band in your transmission. Take it to a transmission shop.