What Is a Transmission Throttle Valve?

by Andrea Stein
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In mechanics, the transmission converts speed and torque from a rotating power source to other devices through the use of gear ratios. The gears, which control the shifting ability of a vehicle, are facilitated by the transmission throttle valve.


The transmission throttle, a mechanism that manages the flow of fluid, contains a butterfly valve. This valve opens or closes to either allow or obstruct the passage of air or fluid and converts line pressure, which is directed to valves in the transmission.

Throttle Cable

The throttle cable refers to a cable device that supplies key throttle input to the transmission. The cable detects gas pedal position by connecting to the gas pedal at one end and the transmission throttle valve at the other. This enables engine speed to be monitored, which, in combination with throttle position, helps determine when the transmission can shift.

Vacuum Modulator

The vacuum modulator device detects engine vacuum via a hose attached to the engine. When high vacuum is produced due to light engine load, the vacuum moves the modulator, which in turn shifts the throttle valve, allowing the transmission to shift earlier. When the engine load increases, the vacuum level decreases, causing the modulator to shift the valve in the opposite direction, enabling the transmission to shift later.

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