I am helping a friend that has a very hard 1-2 shift, and it will not soften no matter how much I try to change it in the tune. It is a 94 with a 350. He has owned the truck for a while, and decided to put a computer in it out of a 2001 Express van. The tranny is completely stock and he never had this problem before the new computer. Does anyone know what we are overlooking? Everything else shifts fine, just the 1-2 shift is the problem.

 

I believe a 94 still had the older pressure control solenoid that operated at a much slower frequency and also had some type of self cleaning procedure built into the control of it. I want to say it ran in the 250-300 hz range and the newer ones like 95 or 96 and newer run in the 500-600 hz range and don't have the self cleaning thing anymore. Some of the guru's should be able to give you all the specifics but I believe this is probably whats causing your issue.