It's just a matter of shortening or lengthening the linkage from the throttle to the transmission, the one that moves as you go from idle to cruise to wide open. Some linkages push, others pull- - - -it depends on the application. Whichever way it works, moving the linkage further in the direction that represents full throttle results in a longer period between shifts, and a part-throttle downshift at a higher speed. Going to full throttle should result in a forced downshift, known as a "kickdown" or "passing gear" as we used to call it. The 1-3 position locks the trans out of 4th. speed until a safety circuit kicks in at very high engine speed to avoid scattering the engine. Some of them also had a safety circuit in manual 2nd. gear that would shift all the way to 4th. regardless of shifter position if a driver insisted on trying to hold the shifter in low range and got the engine screaming.
Jerry
