Chrysler Repair: Chrysler LHS transmission, 1995 chrysler lhs, chrysler lhs

Question
I have a 1995 Chrysler LHS Engine 3.5 Transmission 42LE. The transmission seems to start in 2nd gear and jumps back into 1st gear when in very heavy traffic and on hot days.  It will go for weeks or months without doing this, then when it does it is very severe.  I took it to the Chrysler dealer today and there weren't any "codes". They said changing the transmission control module may fix it, but no guarantee.  It would cost $400.00 The car has never overheated, but the transmission acts like a heat problem.  The radiator has a trans cooler and there is an external cooler as well, both factory installed.  

Answer
The transmission is electronically controlled and it could really be any number of things.  I'm kind of suprised that the dealership wanted to START with a controller because it could be something as simple as a $25.00 speed sensor acting up.  With no codes and no other readings taken from the controller then there's no way of knowing what the problem really is.
Doug