Jeff's 727 rebuild thread
Can you post a picture of the kickdown linkage at the trans where the adjustment is? Was the governor assembly on the output shat modified in any way with the shift kit? I fear that Kickdown is correct about fluid pressure finding it's way past the throttle valve, or maybe even a governor circuit somewhere. Maybe read through the shift kit instructions again and review pictures you took during the disassembly. You may realize a mistake was made that is easy to fix. And don't worry, the trans should not have to come out again. Problem is most likely in valve body or governor assembly, if kickdown linkage is correct. Shift linkage won't cause this.