Transmission – Overview

Design and Function

Applies to: AW50/51 AWD, AW55-50/51SN

AW55-51 is a 5 speed electronically controlled automatic transmission with a lock-up function for the three highest gears. The transmission control module (TCM) adapts the gear changes to ensure that the correct gear is selected for the driving mode, engine load, driver requirements, speed etc. This gives good fuel economy combined with increased comfort by ensuring smoother gear changes and lower noise levels.

In a vehicle with an automatic transmission, the driver neither needs to decide which gear should be used nor shift gear. There is a operating system in the AW55-51 which uses a torque converter and gear shift system to do this.

For information about the transmission control module (TCM) and its functions, see Design and Function, transmission control module (TCM).

Applies to: 2006–2009; M66, M66 AWD

The transmission is intended to be part of a transverse drive line with front wheel or four wheel drive. The transmission and final drive are constructed together in a common housing made of aluminum. The unique design of the transmission and final drive makes it extremely compact, yet capable of transferring high torque.

The engine and transmission have damped mountings, either on the side members with pendulum mounting or on a sub frame.

The gear controls consist of the gear selector assembly, electronic back-up (reverse) inhibitor and two mechanical shift cables which are connected to a lever each on the transmission. The gear selector is not adjustable. However lateral movement can be adjusted. If there is a fault or damage in/to one of the mechanical cables, both must be replaced at the same time.

The gear selector assembly is seated in rubber bushings secured to the floor of the tunnel for efficient sound insulation. The bearings for the gear selector lever in the gear selector assembly and the bearings for the outer mechanical cable controls are permanently lubricated low friction bearings.

The oil is synthetic.

Applies to: 2006–2009; TF-80SC, TF-80SC AWD

TF-80SC (TF-80SC AWD) is an electronically controlled 6-speed automatic transmission 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-80SC 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-80SC 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).