Little help with kickdown on Super Six conv

That spring is important. Its job is to pull the end of the slot against the throttle pin so that as soon as the throttle begins to open, the throttle pressure begins to increase.

Without the spring, there is no throttle pressure increase until the pin hits the slot's end.

That's the whole point of having throttle pressure linkage. So that as soon as the throttle opens and the car accelerates, there is increased throttle pressure to hold the clutches together upon an increase in acceleration.

The linkage should be adjusted with that spring installed and accounted for.

Adjust the linkage so the linkage on the transmission is all the way back when the throttle is completely open and adjust from there if the shifts are too late and or too hard.