Abstract: An actuator for an automatic transmission modulator valve which automatically changes shift speeds proportional to demand on the engine from idle to full throttle. The actuator is preferably controlled by a push-pull cable operatively connected to the throttle or accelerator, and exerts pressure on the push pin of the modulator valve in direct proportion to the travel of the throttle. The actuator utilizes balls between inclined surfaces on interfacing rotary and stationary cam plates and the cable applies rotating force through a moment arm to the rotary plate to obtain a substantial mechanical advantage in the amount of pressure applied to the push pin.