Torqueflite transmissions are equipped with a throttle control lever on the driver's side that fits on a shaft that extends from the valve body. The throttle control lever controls the line pressure of the transmission. The throttle control assembly (also called the kickdown assembly) is connected to the carburetor linkage and pushes back on the throttle control lever depending on the amount of throttle given by the driver. Normally there is no need to adjust the assembly unless it has been disconnected, or the transmission is either shifting too early or won't kickdown to a lower gear when given more throttle at speed. It is extremely important that this assembly be connected and adjusted properly, or it will cause early transmission failure. The ONLY time this assembly should be disconnected is with a full manual valve body setup.
Below, paraphrased from the Factory Service Manual, is the method for adjusting the kickdown linkage:
Make sure that the carburetor fast idle cam is disengaged (in other words, the car should be warmed up)
Make sure that all of the linkage from the carburetor on back is lubricated and moving freely
Make sure that the adjustment swivel on the throttle control rod slides freely back and forth
Loosen the adjustment screw
Pull the throttle control lever on the transmission forward as far as it will go (make sure that the carburetor linkage doesn't move)
Tighten the adjustment screw to 100 inch/lbs and you're done
Source: Chrysler RWD Factory Service Manual Photo: Courtesy of Chrysler Corporation