Transmission

Clutch

The single dry-disc diaphragm clutch is hydraulically actuated. The disc diameter is 230 to 242 mm, depending on the type of engine.
In models fitted with the 2.2 HDi engine, the clutch acts on a twin-damped engine flywheel designed to filter out cyclical vibration at low engine speeds. The 3.0 V6 engine is fitted with a “flexible” engine flywheel.

Manual gearbox

The engines are coupled with an ML5T manual gearbox with gear ratios to suit the type of engine and vehicle characteristics.
The gear change mechanism is cable driven to reduce vibration, and driving comfort is further increased by a specially designed synchromesh lubrication system. The gearbox is lubricated for life (capacity 1.8 litres). Total BV 75W – 80W gearbox oil is recommended.

Automatic gearbox with sequential control

The engines are coupled with a 4HP20 automatic gearbox.  This gearbox is manufactured by ZF and can accept an input torque up to 330 Nm. In addition to a fully automatic mode, this gearbox also offers manual sequential mode.

Manual or sequential mode : In this mode, automatic gear change is disabled and the driver can change at will through the ratios between first and fourth gear, subject to a number of safety overrides including the following :

• changing up a gear below 1,100 rpm is prohibited to avoid engine stalling. Similarly, changing up a gear is not permitted when the engine speed is too low ;

• protection is provided against overheating ;

• changing to a lower gear during sudden acceleration, for example when overtaking.

The driver can select sequential mode at any time when the gearbox selector is in the D (Drive) position. The currently selected gear ratio will then be maintained until the driver decides to move up or down a gear. If sequential mode is deselected, the gearbox will take over and select the most appropriate gear automatically. In low-grip conditions, the driver can select pullaway in second or third gear.

Automatic mode relies on a number of programmed gearshift patterns, to adapt the gearbox automatically to the driving style (economy, medium, sport, etc.), the selected programme 
(sport, snow, etc.), external conditions (road profile, grip, vehicle loading, acceleration and deceleration, etc.) and internal conditions (gearbox oil temperature and pressure, cold engine, etc.).  As well as managing the gearshift patterns, the electronic controller monitors and controls a number of parameters in order to ensure maximum active safety for vehicle occupants and prevent gearbox damage.

The gearbox is fitted with a torque converter with lock up, two epicyclic gear trains with multi-disc clutches and brakes ; hydraulic unit ; water / oil intercooler and, naturally, an electronic controller. The controller dialogues with the engine control unit and inputs data from a number of sensors in order to control the gear-change and lock-up systems. When the engine is idling, the turbine in the torque converter rotates at the same speed as the engine, resulting in a significant reduction in drag, which means lower fuel consumption and vibration.

The selector lever and offset gear grid ensure smooth gear selection. There are four positions in automatic mode : P (Park), R (Reverse), N (Neutral) and D (Drive), plus one position for M (Manual) mode. In this position, the driver can move sequentially up or down through the gears by pressing two buttons (+ and -). Two additional buttons, located just below the selector lever select the “Sport” or “Snow” programmes.As an additional safety measure, the selector position is indicated on the instrument panel.