The Governor Valve
The governor valve is a mechanical valve used in non-electronic hydraulically controlled transmissions. It varies governor pressure proportional to vehicle speed. This means that if the vehicle is traveling at around 20 mph, there should be around 20 psi. in the governor circuit. The output shaft drives the governor valve. As the shaft spins a set of weights moves the valve with centrifugal force. This varies governor pressure.
This valve has been replaced in electronic transmissions by the (VSS) or vehicle speed sensor. The VSS inputs vehicle speed to the TCM. The TCM uses the VSS signal for vehicle speed and the TPS signal for engine load to activate the appropriate solenoid at the correct shift point. The governor and the VSS are related to vehicle speed and the TP sensor is related to engine load.