where is the pcm on a 1998 Mitsubishi Galant es

we've swapped out the tranny on my mitsubishi the old one wouldnt catch gears the new one runs but won't shift gears we can run it upto 80-85mph but the rpms are at about 5ooo almost redlining we've changed the part holding the solenoids out twice already we've changed the sensor under the shift cable and a few other sensors connected to the tranny but the p1750 code continues to show up