Mercedes S-Class W-140

1991-1999 of release

Repair and operation of the car



Mercedes S-Class
+ Mercedes-Benz cars of the class S (W-140)
+ Operation manual
+ Routine maintenance
+ Engine
+ Cooling systems, heating
+ Power supply system and release
+ Engine electric equipment
+ Gear shifting box
- Automatic transmission
   Specifications
   Search of malfunctions - the general information
   + Automatic transmission 722.5
   + Automatic transmission 722.6
+ Coupling
+ Brake system
+ Suspension bracket and steering
+ Body
+ Onboard electric equipment






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 (hydrotransformer), 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.

Design of typical AT

Design of typical AT


1 — the Tube of filling of transmission with oil
2 — Schild
3 — the 13-contact socket
4 — Transmission
5 — a driveshaft Flange
6 — Blocking of position of the parking

7 — Draft of the selector
8 — System of release
9 — the Arm of system of release
10 — Perekladina with a support
11 — the Tire of connection with weight


Section of automatic transmission

1 — the Entrance shaft
2 — ECU
3 — the Intermediate shaft
4 — the Blocking gear wheel of the parking
5 — the Output shaft
6 — the Oil pump
7 — Gidrotransformator
8 — a reactor Shaft
9 — the Blocking hydrotransformer coupling
B1 — Multidisk brake assembly of B1

B2 — Multidisk brake assembly of B2
B3 — Multidisk brake assembly of B3
F1 — F1 Flywheel
F2 — F2 Flywheel
N — Back planetary assembly
K1 — Multidisk coupling of K1
K2 — Multidisk coupling of K2
K3 — Multidisk coupling of K3
M — the Central planetary assembly
V \Forward planetary assembly


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 control system of transmission (known as electronic system of synchronous switching) is a component of the modified control system of the engine installed only on model with AT.

Scheme of an arrangement of electronic components of a control system

Location of the AT (N15/3) control unit. In a motive compartment, on the right at a partition



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 (see the Section Check of Levels of Liquids, control of leakages of the Head Routine maintenance). 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 kickdown mode. Activation of the 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 situation "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).