You are likely right on that. I noticed you don't want to mess with the valvebody, but there really isn't anything intimidating to em. I would for sure get it apart and thoroughly clean all the valves and spools, as that is the number one source for shifting issues with any auto tranny.
We are going to tear it down and clean it. My book shows where all the balls go, but we are going to only take it half at a time so we do not get springs confused... A lot of them look alike.
I've already done this transmission once... last year. I installed a "shift reprogramming kit", but found out that I probably used the wrong directions... using the diesel directions instead of the gas directions. I believe this is what caused this transmission to fail.
Hence the reason why I don't want to monkey with the valvebody too much! I am looking at a different manual valve, though. One that will let the fluid flow to the converter in Park... The kit is $150... -- "F is for Fire that burns down the whole town... U is for Uranium...... Bombs... N is for NO SURVIVORS!!!!!" Sheldon Plankton