Automatic transmission hybrid drive function - GF27.10-P-0002AHO

TRANSMISSION 724.2 in MODEL 212 

Automatic transmission (AT), general 

Transmission 724.2 is an electronically controlled automatic transmission with 7 forward gears and 2 reverse gears. The gear ratios for the gear ranges are achieved by planetary gear sets. All the transmission functions and components for this transmission are combined in one assembly module.

Integration of the fully integrated transmission control controller unit (Y3/8) in the transmission minimizes the number of interfaces to the wiring harness. This improves the shift quality, increases the service life and reliability and also lowers maintenance costs.

Service life can be increased, fuel consumption reduced, gearshift comfort improved and maintenance intervals revised by using optimized transmission components and a new automatic transmission fluid as well as by reducing working pressure and by implementing modified software.

The transmission can be subdivided into the following assemblies:

• Wet clutch with torsional damper
• Oil pump for producing the necessary oil pressure and for safe lubrication of actuators and bearing points
• Electric transmission oil pump (M42) for generating the required oil pressure and for guaranteeing lubrication of actuators and bearing points at engine OFF, hybrid and electric driving mode
• Oil cooling system for optimized short-term heat dissipation
• Transmission housing with mechanical transmission components (planetary gear sets, parking lock mechanism, multidisk clutches and multidisk brakes)
• Electric controller unit (with integrated electrohydraulic park pawl actuation)

The following table presents the model and major assembly overviews for transmission 724.2:

Data is exchanged with the following control units via the drivetrain CAN (CAN C):

• CDI control unit (N3/9) (with engine 651)
• ME-SFI [ME] control unit (N3/10) (with engine 276)

Valid for vehicles up to model refinement package 13 

Data is exchanged with the following control units via the chassis CAN (CAN E) and the drivetrain CAN with the interface of the CDI or ME-SFI [ME] control units:

• Instrument cluster (A1)
• Steering column tube module control unit (N80)
• Regenerative braking system control unit (N30/6)
• Electronic ignition lock control unit (N73)
• Front SAM control unit with fuse and relay module (N10/1)

Data is exchanged with the following control units via the interior CAN (CAN B), the chassis CAN and the drivetrain CAN (with the interfaces of front SAM control unit with fuse and relay module and CDI or ME-SFI [ME] control unit):

• Trailer recognition control unit (N28/1) (with code (550) Trailer hitch)
• Left front door control unit (N69/1)

As of model refinement 13, the existing chassis CAN will be replaced by chassis CAN 1 (CAN E1). An additional chassis CAN 2 (CAN E2) is used between the instrument cluster and the front SAM control unit with fuse and relay module. The ME-SFI [ME] control unit or the CDI control unit is the interface between the drivetrain CAN and chassis CAN 1. The interface between chassis CAN 1 and chassis CAN 2 is formed by the front SAM control unit with fuse and relay module. Data is exchanged with the following control units via the hybrid CAN (CAN L) with the interface of the CDI or ME-SFI [ME] control unit:

• Battery management system control unit (N82/2)
• Power electronics control unit (N129/1)

Further subfunctions are described in separate documents:

• Transmission control, function 
• Key-P function 
• Shift operation, function 
• Power transmission, function 

The electrical transmission oil pump and electrohydraulic park pawl actuation are integrated in the transmission housing. The advantages of this are the increase in installation space, the reduction of the wiring harness as well as the minimization of electromagnetic interference.