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A transmission governor is a device found in older hydraulically controlled automatic transmissions. Its primary function is to regulate the shifting of gears based on vehicle speed. Here’s how it works:
- Location and Function: The transmission governor is typically located on the output shaft of the transmission. As the vehicle accelerates, the rotation of the output shaft increases. The governor responds to this rotational speed and translates it into hydraulic pressure changes within the transmission.
- Governor Pressure: The rotation of the output shaft drives the governor mechanism, which in turn generates a hydraulic pressure known as governor pressure. This pressure is proportional to the vehicle’s speed and is used to actuate various hydraulic valves within the transmission.
- Shift Timing: The governor pressure is fed into the hydraulic control system of the transmission. It influences the timing and firmness of gear shifts by modulating the engagement and disengagement of clutches and bands.
- Shift Points: The design of the transmission governor, including its internal weights and springs, determines the relationship between vehicle speed and gear shift points. As the vehicle accelerates, the governor pressure increases, causing the transmission to upshift to higher gears at predetermined speeds.
- Hydraulic Control: In hydraulically controlled transmissions, the governor plays a crucial role in regulating line pressure and controlling the flow of transmission fluid to the various hydraulic circuits within the transmission.
- Modern Transmissions: In newer vehicles equipped with electronically controlled transmissions (ECT), the role of the governor is largely replaced by electronic sensors and solenoids. These sensors provide input to the transmission control module (TCM) or engine control module (ECM), which then electronically adjust shift points and transmission behavior based on real-time vehicle speed and other parameters.
The transmission governor is a critical component in older hydraulically controlled automatic transmissions, regulating gear shift points based on vehicle speed. While modern electronically controlled transmissions have largely replaced the governor with electronic sensors, it remains an essential part of historical transmission designs.
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