Parking lock

The 8-speed automatic gearbox is equipped with a parking lock to secure the vehicle against rolling away. The mechanism is identical to that of the predecessor. The parking brake blocks by using a locking pawl that engages in the gearing of the parking lock gear. The parking lock gear is located on the output shaft of the gearbox. The parking lock pawl is engaged by spring force. The parking lock is designed to ensure a secure position of the vehicle under the following preconditions:

• Uphill or downhill gradient of up to 32 %
• Speed below 2 km/h

The parking lock must not engage at speeds above 5 km/h. All models are equipped with electric gearshift via the gear selector switch (GWS). The parking lock is engaged by pressing a button or, under certain circumstances, also automatically.

The parking lock is actuated electrically. The notched disc in the gearbox is omitted. It is replaced by a parking disc, a parking lock cylinder, a solenoid valve and a parking lock magnet. A distinction is made between mechanically engaging the lock and associated electric activation. As mentioned above, the parking lock is engaged using spring force. Electric activation of the lock performed by:

• Activation via a button on the selector lever
• Switching the engine off while drive position is engaged
• If, when stationary, selector lever position R or D are engaged and neither the accelerator pedal nor the brake pedal are being operated, the seat belt of the driver's seat is released and the driver's door is opened.

The electronic transmission control (EGS) activates the solenoid valve and the parking lock magnets. The solenoid valve is located in the hydraulic shift unit. The parking lock magnet is located on the cylinder for the parking lock. Upon engaging the parking lock, the parking lock magnet for the parking lock cylinder is switched off. This results in releasing the mechanical lock and the piston. The solenoid valve in the shift unit is also switched off. The valve moves to rest position and the parking lock cylinder is bled. A pre-tensioned helical coiled spring on the parking disc pulls the piston towards the parking lock. The parking lock is engaged using the connecting rod attached to the parking disc.

It is engaged hydraulically. To engage, solenoid valve 2 actuates the parking lock valve so that the system pressure reaches the parking lock cylinder. This pushes the piston back against the spring force and the parking lock is released. The parking lock magnet is additionally actuated. It also locks the piston with a locking mechanism or keeps it in position N when the engine is at standstill. The parking lock is opened only under the following preconditions:

• Engine running
• Footbrake depressed
• Selector lever position in R, D or N