Mercedes S-Class W-220

since 1998 release

Repair and operation of the car

Automatic transmission

General information

Automatic transmission, in the course of start-off from the place, performs function of ordinary coupling, and during the movement performs work on gear shifting.

The AT main hubs are: torque converter, planetary reducer and hydraulic or electronic control system. Hydrodriving disk brakes and disk coupling are applied to transition to another transfer the relation in a planetary reducer.

The torque converter on the functions corresponds to hydraulic coupling. Its task includes implementation of coupling at start-off from the place and gear shifting.

The principles and schemes of construction and functioning of AT are in detail considered in the management "Automatic transmissions of modern cars" of ARUS publishing house.

The control system of transmission (known as system of electronic synchronous switching) is a component of the modified control system of the engine. The control system can work in the special safe mode into which passes at detection of any malfunction. At the same time operating modes of transmission are limited, and the car can be delivered under the own steam to repair shop. Upon transition of a control system to the safe mode on the control panel the control lamp lights up (address the Head the Operation manual). Analyzing information arriving from various sensors (not only the sensors directly related to transmission), the control system chooses optimum from the point of view of profitability, smoothness of the course, etc. a box operating mode. At a certain position of the gate of a throttle the control system can block the hydrotransformer in such a way that only the fourth and fifth transfers will join. It reaches considerable decrease in consumption of fuel.

The only regular procedure of service of a box is check of level of working liquid (address the Section Check of Level of Oil of Automatic Transmission). Regularly it is not necessary to change transmission liquid.

Near a radiator of the cooling system the cooler of transmission liquid is established.

There is no traditional switch of the Kick-Down mode. Inclusion of this mode is carried out directly by a control system of transmission after the information processing arriving from the sensor of provision of a butterfly valve.

There are several operating modes of transmission, each of which can be involved after moving of the selector to one of the following provisions: P, R, N, D, 1, 2, 3, 4 (address the Head the Operation manual).

The engine can be started only if the selector is in the provision of P or N. It is made to prevent the movement of the car in start attempt (if the selector is installed in one of other provisions). Analyzing information arriving from sensors, the control system resolves or forbids start of the engine. The locations of various relays are specified in the Head Onboard electric equipment.