Which pressure provides a speed-sensitive signal to the control valve body?

• A. MPRV pressure
• B. Modulator pressure
• C. Governor pressure
• D. Main pressure

Answer: (C)

Speed sensing in an automatic transmission is provided by governor pressure. The governor, driven by the output speed, has weights that move outward as speed rises. This movement opens a valve and increases the governor pressure, which becomes the signal that tells the valve body how fast the vehicle is going. The control valve body uses this speed signal to time shifts and adjust line pressures accordingly. Other pressures have different roles: main pressure is the overall hydraulic supply, and modulator pressure comes from the modulator (often vacuum or engine-load related) to affect shift feel, not to indicate speed. So the governor pressure is the speed-sensitive signal the valve body uses.