transmission won't shift in to drive

[sacreech2000]

just had a motor and trans put into 99 grand am gt the motor and trans was out of a 2004 the transmission will shift up some mornings but later in the day it will only shift up to 3rd when driving 60 my rpm's is about 2200 the new trans only has 16,000 miles help

[GTP Dad]

Welcome to AF!!

Did you change the transmission computer when you changed engines. The transmission is computer controlled and if the computer you are using from the 1999 is not compatable that can prevent it from shifting properly.

[sacreech2000]

Originally Posted by GTP Dad

Welcome to AF!!

Did you change the transmission computer when you changed engines. The transmission is computer controlled and if the computer you are using from the 1999 is not compatable that can prevent it from shifting properly.

where is the computer located at and how hard is it to change