What causes a transmission to run good cold and bad when its hot?
not enough fluid, check the fluid level while the car is hot and
in nuetral. Another thing to watch for suprisingly enough, is the
speed sensor. Mine does'nt shift when warm, and also the
speedometer needle won't move when it starts to act up. Was told if
the speed sensor is'nt working it won't let the computer know
you're moving, so it thinks your stopped so stays in first gear,
even though you're driving. I thought it was a tranny problem,
butnow know it was'nt. Something for you to think about or ask
about before purchasing a new transmition.