Chevrolet Equinox Service Manual: Transmission General Description Automatic Transmission Unit

The Hydra-matic 6T40/45/50 is a fully automatic, 6-speed, front-wheel drive, electronic-controlledtransmission. It consists primarily of a 4-element torque converter, a compound planetarygear set, friction and mechanical clutch assemblies, and a hydraulic pressurizationand control system. There are 2- variants of the transmission, based on torque capacity.Architecture is common between the variants, and component differencesare primarily related to size.

The 4-element torque converter contains a pump, a turbine, a pressure plate splinedto the turbine, and a stator assembly. The torque converter acts as a fluid couplingto smoothly transmit power from the engine to the transmission. It also hydraulicallyprovides additional torque multiplication when required. The pressure plate, whenapplied, provides a mechanical direct drive coupling of the engine to the transmission.

The planetary gear sets provide the 6-forward gear ratios and reverse. Changing gearratios is fully automatic and is accomplished through the use of a transmission controlmodule-(TCM) located inside the transmission. The TCM receives and monitors variouselectronic sensor inputs and uses this information to shift the transmission at theoptimum time.

The TCM commands shift solenoids and variable bleed pressure control solenoids tocontrol shift timing and feel. The TCM also controls the apply and release of thetorque converter clutch which allows the engine to deliver the maximum fuel efficiencywithout sacrificing vehicle performance. All the solenoids, including the TCM, arepackaged into a self-contained control solenoid valve assembly.

The hydraulic system primarily consists of a gear-type pump, a control valve bodyassembly and case. The pump maintains the working pressures needed to stroke the clutchpistons that apply or release the friction components. These friction components,when applied or released, support the automatic shifting qualities of the transmission.

The friction components used in this transmission consist of 5-multiple disc clutches.The multiple disc clutches combine with one way clutch to deliver 7-different gearratios, 6-forward and one reverse, through the gear sets. The gear sets then transfertorque through the transfer drive gear, transfer driven gear and differential assembly.

The transmission may be operated in any of the following gear ranges:

This position locks the front wheels and prevents the vehicle from rolling eitherforward or backward. PARK is the best position to use when starting the vehicle. Becausethe transmission utilizes a shift lock control system, it is necessary to fully depressthe brake pedal before shifting out of PARK. For safety reasons, use the parking brakein addition to the PARK position.

This position allows the vehicle to be operated in a rearward direction.

This position allows the engine to be started and operated while driving the vehicle.If necessary, you may select this position in order to restart the engine with thevehicle moving. This position should also be used when towing the vehicle.

Drive range should be used for all normal driving conditions for maximum efficiencyand fuel economy. Drive range allows the transmission to operate in each of the 6-forwardgear ratios. Downshifts to a lower gear, or higher gear ratio, are available for safepassing by depressing the accelerator or by manually selecting a lower gear in themanual mode range.

This position-(M–Manual-/-L–Low) allows the driver to utilize the-DSC/ERS system.When the shift selector lever is moved to this position, the driver may select upshiftsor downshifts by using the paddle switches located on the steering wheel/shifter.An upshift is requested by pushing either + button. Refer to thevehicle owner's manual for more specific DSC/ERS information.