Transmission General Description

Transmission General Description

The Hybrid Two-Mode 2ML70 is a fully automatic, variable-speed, rear-wheel drive, electronic-controlled transmission. It consists primarily of a torque dampener assembly, an integral fluid pump and converter housing, 3 planetary gear sets, 2 friction (rotating) and 2 mechanical (stationary) clutch assemblies, and a hydraulic pressurization and control system, and 2 internal concentric 60 KW electric motors.

The torque dampener contains an internal torsional springs, fluid, input shaft. The torque dampener acts as a spring coupling to smoothly transmit power from the engine flexplate to the transmission. The dampener provides a mechanical direct drive coupling of the engine to the transmission.

The planetary gear sets provide 4 fixed gear ratios and the 2 EVT forward modes rations and reverse. Changing gear ratios is fully automatic and is accomplished through the use of a transmission control module (TCM) located inside the transmission and the hybrid powertrain control module (HPCM) located under the hood. Both the TCM and HPCM receives and monitors various electronic sensor inputs and uses this information to shift the transmission at the optimum time.

The TCM commands shift solenoids and variable bleed pressure control solenoids to control shift timing and feel. All the solenoids, including the TCM, are packaged into a self-contained control solenoid valve assembly.

The main hydraulic system primarily consists of a vane-type pump, 2 control valve body assemblies, converter housing and case. The pump maintains the working pressures needed to stroke the clutch pistons that apply or release the friction components. These friction components, when applied or released, support the automatic shifting qualities of the transmission.

The hydraulic system also uses a secondary system and consists of an auxiliary pump attached to the bottom of the transmission. This is a gerotor-type pump, electric 3 phase 12 volt motor, electric harness, and control module. This pump maintains working pressures when the engine is off.

The friction components used in this transmission consist of 4 multiple disc clutches. The multiple disc clutches combine with a planetary gear set and electric motor to deliver the different gear ratios, forward and 1 electric reverse. The gear sets then transfer torque through the output shaft.

The transmission may be operated in any of the following gear ranges:
PARK (P)
- This position locks the rear wheels and prevents the vehicle from rolling either forward or backward. PARK is the best position to use when starting the vehicle. Because the transmission utilizes a shift lock control system, it is necessary to fully depress the brake pedal before shifting out of PARK. For safety reasons, use the parking brake in addition to the PARK position.

REVERSE (R)
- This position allows the vehicle to be operated in a rearward direction. This is done by the drive motor with generator 2nd position and is electric only. Note: the engine will start when shifted to reverse.

NEUTRAL (N)
- 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 the vehicle moving. This position should also be used when towing the vehicle.

DRIVE (D)
- Drive range should be used for all normal driving conditions for maximum efficiency and fuel economy. Drive range allows the transmission to operate in each of the 4 forward gear ratios and 2 EVT modes gear ratios. Downshifts to a lower gear, or higher gear ratio, are available for safe passing by depressing the accelerator or by manually selecting a lower gear in the manual mode range.

Manual (M)
- This position allows the driver to utilize the Driver Shift Control (DSC) system, or manual mode. When the shift selector lever is moved to this position, the driver may select upshifts or downshifts by using the paddle switches located on the gear shift lever. An upshift is requested by pushing the + button. A downshift is requested by pulling the - button. Refer to the vehicle owner's manual for more specific DSC information.