Automatic transmission (AT), function - GF27.10-P-0001SX

TRANSMISSION 722.9 in MODEL 216, 221 up to Model Year 8

Fig 1: Identifying Automatic Transmission (AT) Function Diagram

Courtesy of MERCEDES-BENZ USA

Networking of components, shown on model 221.054 with engine 272, except code (494) USA version, except code (219) Distronic (DTR)

Fig 2: Identifying Networking Function Diagram

Courtesy of MERCEDES-BENZ USA

Transmission 722.9 is an electronically controlled automatic transmission with 7 forward gears and 2 reverse gears. All the transmission functions and transmission components for this automatic transmission are combined in one assembly module. Integrating the electrohydraulic controller unit in transmission 722.9 minimizes the number of interfaces to the wiring harness. The electrohydraulic controller unit is installed below the transmission housing; the transmission oil is continuously flushed around the outside of the controller unit, which amongst other things, ensures the controller unit is cooled.

Transmission 722.9 can be roughly divided into the following component groups:

Torque converter with torsional damper and torque converter lockup clutch.
Oil pump to produce the necessary oil pressure and for reliable lubrication of the actuators and bearing points.
Transmission housing with transmission mechanism and the electrohydraulic controller unit. The transmission housing is made of a light alloy.
The mechanical transmission components, consisting of a Ravigneaux gear set, front single planetary gear set, rear single planetary gear set and a park pawl. Additionally, a multi-disk clutch K1, multi-disk clutch K2, multi-disk clutch K3, multi-disk brake B1, multi-disk brake B2, multi-disk brake B3 and the BR multi-disk brake are also integrated. Single-sided disks are used on multidisk clutch K1, on multidisk clutch K2 and on multidisk clutch K3 Single-sided disks are also used on multidisk brake B1 and on multidisk brake B3 On this type of lamella the friction lining is only applied on one side. Among other things, this improves heat distribution in the disk pack, the design of the disk pack is more compact, the load-bearing capacity is increased and the mass is reduced. For the multi-disk brake B2 and BR multi-disk brake disks coated on both sides are also used.
The electrohydraulic controller unit, consisting of the electric controller unit (VGS) (Y3/8), the valve body and the valve housing.

The following information are taken into account when shifting the drive positions:

Vehicle speed
Vehicle load
Driving resistance
Position and operating speed of accelerator pedal
Selected drive position and engaged gear
Selected transmission mode
Oil temperature and other information about the status of the transmission
Further signals which are available via the Controller Area Network (data bus/CAN bus) (CAN)

Via CAN data is exchanged with the following control units and controls:

Instrument cluster, via the central-CAN
Intelligent servo module for DIRECT SELECT, via the drive train CAN
DTR controller unit (A89), on vehicles with code (219) Distronic (DTR), via the vehicle dynamics CAN
Front central operating unit, via the telematics CAN
CDI control unit (N3/9), via drive train CAN, on model 221 with engine 642 or engine 629
ME control unit, via drive train CAN, on model 216, on model 221 except engine 642 or engine 629
ESP control unit, via the chassis CAN
EIS [EZS] control unit, via the chassis CAN
Steering column module, via the chassis CAN
Central gateway control unit, via the chassis CAN

On model 221 the ME control unit or CDI control unit forms the interface between the drive train CAN and the chassis CAN. On model 216 the ME control unit forms the interface between the drive train CAN and chassis CAN. The central gateway control unit is amongst others the interface between the chassis CAN and central CAN, the COMAND controller unit is the interface to the telematics CAN and the ESP control unit is the interface to the vehicle dynamics CAN.

This involves the processing of the following data from other systems:

Front central operating unit

Transmission mode selection at transmission modes button (A40/9s8) (model 216)
Transmission mode selection at transmission modes switch (model 221)

ESP control unit

Vehicle lateral acceleration at center of gravity, adaptation of shift strategy, detection of dynamic driving style
Wheel speeds and direction of rotation, substitute values in event of malfunction of output speed sensor (VGS) (Y3/8n3)
Adjusted brake torque, change in shift strategy, brake the vehicle, fully integrated transmission control (VGS) shifts down sooner
Cruise control controls, a special shifting strategy for cruise control mode is filed in the fully integrated transmission control (VGS) control unit
Electronic Stability Program (ESP) desired, shift mechanism in "N" (Neutral), power flow interruption, rear axle transmission
BAS release switch (A7/7s1), change of shift strategy, brake the vehicle, the fully integrated transmission control (VGS) shifts down earlier

Intelligent servo module for DIRECT SELECT

Actual position of range selector lever

DTR controller unit, on vehicles with code (219) Distronic (DTR)

Shift line displacement, brake the vehicle, the fully integrated transmission control (VGS) shifts down earlier
Active downshift, brake the vehicle, fully integrated transmission control (VGS) shifts down sooner

CDI control unit, on model 221 with engine 642 or engine 629

Start-off in 1st gear, aids engine warm-up
Shift line displacement, aids engine warm-up
Specified gear, lower and upper limit, aids engine warm-up
Engine coolant temperature, used as substitute value in event of malfunction in transmission oil temperature sensor (VGS) (Y3/8s2)
Emergency operation of the common rail diesel injection, the pedal value is limited to approx. 20 %, the driveability of the vehicle is assured
Engine oil temperature, shift limitation is canceled
Request "torque converter lockup clutch OPEN", in the warm-up phase of the engine, to increase engine speed
Shift line displacement, dependent on load condition of diesel particulate filter (DPF), a heavily loaded DPF results in slightly lower upshift speed for full-load and kick-down upshifts
Requirement torque for Electronic Stability Program (Electronic-Stability-Program) (ESP), torque reduction or torque increase taking into account directional stability and road adhesion
Kickdown
Pedal value
Engine torque
Engine idle specified speed for the actuation of the torque converter lockup clutch
Engine-speed limitation function active, adaptations are deactivated in the fully integrated transmission control (VGS) control unit
Engine speed, for slip calculation of torque converter lockup clutch and for start of pressure calculation by fully integrated transmission control (VGS) control unit

ME control unit, on model 216, on model 221 except engine 642 or engine 629

Active downshift for heating up the catalytic converter (TWC)
Start-up in 1st gear for warming up catalytic converter
Shift line displacement to heat up the catalytic converter
Engine oil temperature, shift limitation is not active
Selected torque ESP, torque reduction or increase taking directional stability and road adhesion into account
Specified gear, lower and upper limit to heat up the catalytic converter
Emergency operation of ME gasoline injection and ignition system (motor electronics) (ME), the pedal value is restricted to approx. 20 %, the vehicle driveability is thus assured
Request for torque converter lockup clutch "Open" to increase engine speed in the heating up phase of the catalytic converter
Engine speed, for slip calculation of torque converter lockup clutch and for start of pressure calculation by fully integrated transmission control (VGS) control unit
Engine coolant temperature, used as substitute value in event of malfunction in transmission oil temperature sensor (VGS)
Engine idle specified speed for the actuation of the torque converter lockup clutch
Engine torque
Kickdown
Pedal value

EIS [EZS] control unit

Enable of stage 3 drive authorization system (DAS 3)
Request of Key-P function
Circuit 50, influencing fault memory

Steering column module

Signal from steering wheel gear shifter MINUS (S110/1), on model 216.377, model 221.077/177
Signal from steering wheel gear shifter PLUS (S111/1), on model 216.377, model 221.077/177

Signal from left steering wheel gear shifter, on model 216.371, model 221 0/1 except model 221.077/177
Signal from right steering wheel gear shifter, on model 216.371, model 221 0/1 except model 221.077/177
Signal from DIRECT SELECT gear selector switch

Central gateway control unit

Diagnosis

The following information is passed to other systems: Instrument cluster

Gear selector switch position and programmed shift range for the gear indicator (A1p12)
Transmission mode selection for the transmission mode display (A1p16)