Description And Operation

DESCRIPTION 

The valve body internal to the transmission includes the Transmission Control Module (TCM), all solenoids and sensors, and can be referred to as the Transmission Control Module Assembly (TCMA). The TCM is attached to the valve body between the transmission case and the valve body. If any component of the valve body including the TCM  sensors or solenoids needs to be replaced, the complete TCMA (valve body) must be replaced. For further information of the TCMA. Refer to VALVE BODY, REMOVAL AND INSTALLATION, 8HP50/850RE and/or VALVE BODY, REMOVAL AND INSTALLATION, 8HP75

OPERATION 

The valve body, which includes the Transmission Control Module (TCM), controls the delivery and pressure of transmission fluid. The TCM is integrated into the valve body. The TCM regulates the amount of hydraulic pressure used to engage the clutches and the Torque Converter Clutch (TCC), in addition to directing hydraulic pressure to engage or release any given clutch for any given required gear. The TCM will actuate the valves via solenoids based on the position of the shifter, transmission fluid temperature, engine operating conditions, traction conditions and driver demands. During a shift, the TCM will actuate the solenoids to match the gear ranges to the optimal torque range of the engine based on the position of the accelerator pedal, shifter and vehicle speed as determined by the Powertrain Control Module (PCM) based on input from the Vehicle Speed Sensor (VSS) signal from the Antilock Brake System (ABS) module. Due to the complexity of the transmission control system, always refer to the transmission electrical/electronic diagnostics in this service information when attempting to diagnose transmission problems.

If the Transmission Control Module Assembly (TCMA) is replaced, it must  be programmed and a drive learn needs to be performed before returning the vehicle to the customer.