Transmission Control Systems: Description and Operation

System Description, Tiptronic G51
The mechanism of the automatic transmission works according to the planetary gear principle.

Control is hydraulic electronic where the hydraulic control unit is mounted onto the transmission and the electronic control module is located in the vehicle.

Power is sent to the transmission by means of a hydrodynamic torque converter with integrated torque converter lockup clutch.

Gear selection is carried out by means of the selector lever which is connected to the hydraulic switching device. At the same time, the positions P, R, N, D, M are supplied to the electronic control module in coded form by means of a switch (position switch) secured to the transmission selector shaft. By changing the control speed of the accelerator pedal, the shifting point characteristic can be changed from very comfortable and economical to very sporty and power-conscious. If the selector lever is moved from position D to position M, the current gear is retained. Manually actuated upshifting and downshifting are monitored by the Tiptronic control module and are not accepted if above or below limit speeds.