Transmission – Overview

Design and Function

Transmission TF-80SD

TF-80SD is an electronically controlled 6-speed automatic gearbox with Geartronic.

The Geartronic function combines two transmissions in one. One adaptive 6-gear automatic transmission which enables relaxed driving, and a "manually" shifted transmission which enables more active driving with manual shifting. In case of manual shifting, the gear selector is pushed forward to upshift to a higher gear and it's pulled back to downshift to a lower gear. However, in certain situations the Transmission control module (TCM) assumes the gearshifting decisions. For more information about shifting with Geartronic, see Design and Function, Transmission control module (TCM).

TF-80SD has a lock-up-function on all forward gears except 1st gear. The torque converter has a locked and slipping lock-up-function.

Gearshifts are controlled by an hydraulic operating system. Gearshifts take place without freewheeling and completely automatically in terms of load and speed.

TF-80SD has two planetary train units, a front and a rear, whose shifts are controlled by a number of clutches and brakes. The rear planetary train is of the Ravigneaux type.

The oil level is checked by level pipe (the transmission does not have a conventional dipstick).

The transmission has a total of 8 solenoids that control the hydraulic flow. 6 of these solenoids control the shift process, 1 solenoid controls the torque converter's lock-up function and 1 solenoid controls the system pressure.

The gear selector sensor is integrated in the Transmission control module (TCM). The Transmission control module (TCM) is integrated in the transmission. For information about the Transmission control module (TCM), solenoids and sensors, see Design and function, Transmission control module (TCM).

An electric oil pump is located on the converter cover beside the control system on the front edge of the transmission. The oil pump function is to ensure that the correct pressure and flow are maintained to the gearbox during automatic start/stop which is controlled by the transmission control module (TCM). In the event of a fault in the oil pump the automatic start/stop function stops.