engine/tranny problem

I got a 95 neon and I just change out the tranny to a different one from a 96. the problem is when I start the car the mph rev high to like 30-40 mph and when I put to Park or neutral. It goes to zero. so what is the problem if anybody know?? Am I missing a plug or is the tranny good or not??. thanks

TPS or IAC motor.

TPS or IAC motor.

my tps and iac seem to be intact.. and i still getting the high revin. is it anything got to do with my transmission or is it one of my sensor?

does my speed sensor got something to do with it??

We need more info. Can you put the car in gear and drive it around? When you say the revs go to 30-40 mph, do you mean the engine revs that high,? or the speedometer reads that high,? or is the car going at that speed? And will the engine idle normally when the tranny is in Drive?
I dont know if the speed sensor would cause this or not. You might want to check whether its connectors is fully seated. Its not easy to see or reach unfortunately.