With a correct GM type ratcheting adjuster, which are very common in the aftermarket and work just as well its like this.
The adjuster has a cable lock that firmly attaches to the cable. When setting up a new cable you push the barrel all the way into the housing of the adjuster (the "D" looking shiny metal is a button, press it to release the ratchet to push the barrel into the housing). Lock the cable to the adjuster with no throttle, but no slack in the cable, finger pulled tight is good. Doesnt have to be super tight, the cable. With the engine off push down on the throttle to floored. Its set! That easy.
Whats it doing? When all conditions are OFF. No engine, no throttle and the center of the ratchet barrel is fully in its at a steady state. When you depress the throttle the ratcheting cable adjuster pulls the center of the adjuster, what I call the barrel out to its maximum distance for YOUR full throttle motion. What that does is sets the low side (idle) and the high side (full throttle). The adjuster if its built from the GM design, is set.
I have played with the system some just to get an understanding. Careful to NOT drive the car under a poor condition. If you pull too much (force and disengage the automatic ratchet) on the cable you make the trans shift late (forcing it to think you are at full throttle when you are at light throttle) and will end up going no where as the torque converter spins up, the trans never shifts up.
Too much slack in the cable will make the trans stay in gear too long and again, spins the TQ converter and it will be drivable but will be a dog.
Use the specified adjustment process and it will shift just fine.
BUT!! The carb or TB linkage should be considered. I have an odd linkage so thats the only reason I was chasing the shifting.
A sure way to map the shifting is with fluid pressures off the trans. I had such a hard time I ended up routing a high pressure line to a gauge in the passengers compartment. If you do this (and I dont recommend it for the new to car guy) you need to gather up the operating pressures of the trans. I got the recommended pressures and dialed in the trans with the gauge. Now yer not supposed to keep the gauge in place but I got lazy. I need to remove it. 270 psi of trans fluid is NOT what you want in yer passengers compartment. JR
