Mercedes-Benz ML320. Manual — part 205

Fig. 159: Function Of Torque Converter Lockup Clutch Control
Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

2001 Mercedes-Benz ML320

1998-03 AUTOMATIC TRANSMISSIONS Complete Transmissions - ML 320 - 722.662

me

The aim of using the torque converter lockup clutch is to reduce the fuel consumption and exhaust gas
emissions of the vehicle by reducing torque converter slip. See Fig. 159. This stands in contradiction to the ride
comfort demands made on the drive train with regard to its vibration behavior. The task of the electronic
transmission control is therefore to close the clutch in all driving situations relevant to fuel consumption, if
possible, and ensure that the engine vibrations are isolated from the drive train.

The characteristic curves shown in the diagram illustrate the different operating states of the torque converter
lockup clutch in relation to the accelerator pedal position and transmission output speed, plotted for one
transmission gear.

In addition to the evaluation of these characteristics, the status of the torque converter lockup clutch is also
determined by other variables.

Variables influencing the states of the torque converter lockup clutch:



Accelerator Pedal Movement



Uphill And Down Hill Gradients



Transmission Shift Functions



ATF Temperature



Durability Requirements



Load Condition



Engine Control Influences

Torque Converter Lockup Clutch Control Pressure, Function

See TORQUE CONVERTER LOCKUP CLUTCH CONTROL PRESSURE, FUNCTION.

Torque Converter Lockup Clutch Control Pressure, Function

Apart from extreme states of open or closed, it is possible to operate the torque converter lockup clutch with
preset slip speeds. To enable this variable control pressure must be applied to the torque converter lockup clutch
regulating valve.

The torque converter lockup clutch control pressure is adapted to each operating state via the pulse-width
modulated torque converter lockup solenoid valve (Y3/6y6) which is actuated by the ETC control unit (N15/3).

Torque Converter Lockup Clutch PWM Solenoid Valve, Location/Task/Design/Function

See LOCATION/TASK/DESIGN/FUNCTION OF PWM SOLENOID VALVE, TORQUE
CONVERTER LOCKUP CLUTCH.

Torque Converter Lockup Clutch, Location/Task/Design/Function

See TORQUE CONVERTER LOCK-UP CLUTCH, LOCATION/TASK/DESIGN/FUNCTION.

Torque Converter Lockup Clutch Regulating Valve, Location/Task/Function

2001 Mercedes-Benz ML320

1998-03 AUTOMATIC TRANSMISSIONS Complete Transmissions - ML 320 - 722.662

me

See TORQUE CONVERTER LOCKUP CLUTCH REGULATING VALVE,
LOCATION/TASK/FUNCTION.

Kick-Down Function (Up To 5/31/02) (With Touch Shift)

Transmission With Touch Shift 722.6 In Model 163

Fig. 160: Kick-Down Function (Up To 5/31/02)

2001 Mercedes-Benz ML320

1998-03 AUTOMATIC TRANSMISSIONS Complete Transmissions - ML 320 - 722.662

me

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Operation

The driver's wish for maximum acceleration of the vehicle is met with the kick-down function. See Fig. 160.

When the kick-down switch (S16/6) is operated a CAN Signal is passed on from the electronic selector lever
module control module (N15/5) to the ETC control module (N15/3) via the electronic accelerator.

Based on this information the ETC control module (N15/3) actuates the solenoid valves so that the upshifts and
downshifts take place at higher engine speeds in order to achieve maximum performance.

Kick-Down Switch, Location/Task/Design

See KICK-DOWN SWITCH, LOCATION/TASK/DESIGN.

Hydropneumatic Transmission Control, Function (Without Touch Shift)

Operation

The hydropneumatic transmission control is divided into electronic and hydraulic transmission control.

While the electronic transmission control is responsible for gear selection and for matching the pressures to the
torque to be transmitted, the transmission's power supply control occurs via hydraulic elements in the
electrohydraulic control module. The oil supply to the hydraulic elements, such as the hydrodynamic torque
converter, the shift elements and the hydraulic transmission control, is provided by way of an oil pump
connected with the torque converter.

The electronic transmission control (ETC) allows for the precise adaptation of pressures to the corresponding
operating conditions and to the engine output during the gearshift phase, resulting in a noticeable improvement
in shift quality.

It is possible to reach the engine RPM limit in the individual gears using full throttle and kick-down. The shift
range can be changed in the forward gears while driving, but the electronic transmission control (ETC) employs
a downshift safeguard to prevent over-revving the engine.

The system offers the additional advantage of flexible adaptation to different vehicle and engine variants.

ETC Control Module, Location/Task

See ETC CONTROL UNIT, LOCATION/TASK.

Electric Control Module, Location/Task/Design/Function

See ELECTRONIC CONTROL MODULE, LOCATION/TASK/DESIGN/FUNCTION.

Kickdown Switch, Location/Task/Design/Function Model 163 Without Touch Shift

2001 Mercedes-Benz ML320

1998-03 AUTOMATIC TRANSMISSIONS Complete Transmissions - ML 320 - 722.662

me