When the car is at wot and its sorta cold outside the tranny wont shift outta second gear into third. in the warm weather it doesnt get bothered.

The car always used to shift no matter what the temperature is. i have a trans am stock tranny at 122000 miles. with a converter and tranny cooler

 

I would suspect a restricted or sticking 2-3 solenoid. I would service the trans and replace that at the same time

 

service meaning change the fluid?

 

yes servicing is changing the fluid.