Like FixKick wrote, it may be a Transmission Control Module issue. When you change/alter the valve body springs, it changes the shift points and the TCM
may not be happy with that. When I used to do the all mechanical GM automatics, I liked the extra pressure for the shifts, but for street use, I never liked
how the shift kit held the 2-3 shift for so long so I would always keep the original spring. I would try to get it to work with a stock unit because if you have a computer controlled engine then the ECU may not be happy with your changes. I looked a bit, there is lots on info on modification of that transmission, a number of people say for a street car don't go too crazy on your reprogramming. Anyway, all I wrote is just a guess.
may not be happy with that. When I used to do the all mechanical GM automatics, I liked the extra pressure for the shifts, but for street use, I never liked
how the shift kit held the 2-3 shift for so long so I would always keep the original spring. I would try to get it to work with a stock unit because if you have a computer controlled engine then the ECU may not be happy with your changes. I looked a bit, there is lots on info on modification of that transmission, a number of people say for a street car don't go too crazy on your reprogramming. Anyway, all I wrote is just a guess.