General information

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Fig 1: Transmission Control Module (TCM), 4T65EV-GT System Overview

Courtesy of VOLVO CARS OF NORTH AMERICA.

4T65EV (-GT) is an electronically controlled automatic transmission with an optional lock-up function on the three highest gears. The transmission control module (TCM) adapts the gear shifts so that the correct gear is always selected to match the driving style, engine load, the wishes of the driver, vehicle speed etc. This ensures good fuel economy and increased comfort through smoother gear changes and lower sound levels.

The transmission control module (TCM) receives information about the desired gear position and driving mode from the driver. Unlike with a purely hydraulically controlled transmission, this information, in conjunction with the signals from a number of sensors in the transmission and the engine control system, allows the control module to calculate the optimal shifting points and engagement of torque converter lock-up. The control module allows for small changes in the operating conditions and adapts the various transmission functions to ensure that the correct gear is always selected in relation to the driving mode selected by the driver.

This adaptability guarantees smooth and consistent gear shift quality throughout the operational life of the transmission.

In order to precisely determine the gear shift and lock-up engagement points based on the driving mode selected, the control module receives information about the following:

Selected gear position - from the gear-shift position sensor, which is positioned on the inside of the transmission housing
Selected driving mode - reactive function programmed in the control module which is controlled by the speed at which the accelerator pedal (AP) is depressed. Quick "pedal movement" = sport mode
Vehicle speed - from the brake control system via the Controller area network (CAN)
Transmission input shaft RPM - from the transmission speed sensor
The transmission output shaft RPM - from the transmission output speed sensor
The engine speed (RPM) and torque signal - from the engine management system via the control area network (CAN)
If the brake pedal is depressed - from the brake system via the control area network (CAN)
Accelerator pedal (AP) and movement speed - from the engine management system via the control area network (CAN)
The transmission fluid temperature - from the temperature sensor in the transmission.