Automatic Transmission/Transaxle: Description and Operation

6-Speed Automatic Transmission 09L

Transmission

The 6-speed automatic transmission 09L (all wheel drive) has six hydraulically activated forward gears. When the lock-up clutch is closed these forward gears bypass the torque converter slip and become mechanically driven gears.

Torque Converter

The torque converter is equipped with a slip-controlled torque converter lock-up clutch.

Mechatronic

The mechatronic unit incorporates the hydraulic control, the electronic Transmission Control Module (TCM) (J217), the Multi-Function Transmission Range (TR) Switch (F125) and the sensors and actuators as a complete synchronized unit. The mechatronic unit is installed in the transmission in the area of the oil pan.

Transmission Control Module (TCM) ( J217)

The control module is part of the mechatronic unit in the transmission.

Determining the driving situation and driving resistance dependent shift point occurs automatically.

Advantages:

• It is shifted depending on consumption;

• Maximum engine output is always available;

• Individual adaptation of shift points in all driving situations;

• Gear shift points are infinitely variable.

On Board Diagnostic (OBD)

Before performing service work on the automatic transmission, cause of damage must be determined as close as possible via "Guided Fault Finding".

"Guided Fault Finding" is performed using Vehicle Diagnosis, Testing and Information System (VAS 5051 A).

Shift Point Changes on Inclines and Declines

An additional gear change map automatically selects gear changes for gradients dependent upon accelerator pedal position and driving speed.

• Gear change map for extreme uphill stretches is matched to engine output

• Gear change map for extreme downhill stretches is matched to the braking effect of the engine

• Direct gear selection by way of the Tiptronic function permits utilization of engine braking action with a specific gear engaged, e.g. on a downhill gradient with a trailer