wont shift gears form low on 1990 Mercury Grand Marquis

this is the second tranny i am putting in it will not shift form low gear when driving there is no modulator on it but i have changed the speed control sensor i was told there may be a computer somewhere that controls the shifts if so where if not what controls the shifting it has a 5.0l eng. and a aod tranny automatic

2 answers
check your map sensor. some of those years have a maf for the engine & a map for the tranny. if no map, clean the maf because the map in later years is computed from maf.
My shift gear is hard to move. I have an automatic transmission. What could this be?