The Governor Valve

The Governor Valve vs VSS

The governor valve is a mechanical valve used in non-electronic hydraulically controlled transmissions. It varies governor pressure proportional to vehicle speed. If the vehicle is traveling around 20 mph, there should be around 20 psi in the governor's circuit. The output shaft drives the governor valve. As the shaft spins, a set of weights move the valve with centrifugal force changing governor pressure.

Throttle Position Sensor

Automatic transmission modulator vs throttle position sensor.

This valve has been replaced in electronic transmissions by the (VSS) Vehicle Speed Sensor. The TCM uses the VSS signal for vehicle speed and the (TPS) Throttle Position Sensor signal for the engine load. Both of these sensors affect shift point timing. The governor and the VSS are related to vehicle speed, and the modulator and the TPS are related to engine load.