TCC Enable Valve – When the TCC is in the released condition, torque converter pressure is directed through the valve and into the converter feed limit circuit to the control valve. If the TCC control valve becomes defective and stays at the TCC apply position when the TCC solenoid is de-energised, the converter feed limit pressure enters the release side of the TCC and prevents TCC overheating. When the TCC solenoid is energised, signal pressure from the regulator valve moves the enable valve against the spring force and allows regulated pressure to be directed to the TCC control valve and into the TCC apply circuit. Fluid Pump The fluid pump is an integral part of the transmission. The fluid pump is used to supply hydraulic pressure for control valve and clutch operation and also to pass the fluid through the transmission fluid cooler. The LE fluid pump is a vane type pump which is driven from a direct coupling with the torque converter impeller. The fluid pump rotational speed is therefore governed by the engine speed.
AUTOMATIC TRANSMISSION – GM 5L40-E DESCRIPTION AND OPERATION 44-1-21