Transmission control, function - GF27.60-P-2002GGA

TRANSMISSION 722.902 in MODEL 463.306/336/346 up to 31.5.12 as of Model Year 2011/YoM 10

TRANSMISSION 722.904 in MODEL 463.202/222/236/237 up to 31.5.12 as of Model Year 2009/YoM 08

TRANSMISSION 722.902 in MODEL 463.303/340/341 up to 31.5.12 as of Model Year 2009/YoM 08

Fig 1: Transmission Control Function Diagram

Courtesy of MERCEDES-BENZ USA

Function requirements for transmission control, general

Circuit 87 ON
Function test of fully integrated transmission control unit (VGS) carried out

Transmission control, general

The transmission control system electronically actuates the actuators (control solenoid valves). The valves are positioned on the electric controller unit (VGS). This implements the hydraulic functions. The function of the electric controller unit (VGS) is primarily to evaluate various input signals that are relevant to transmission operation. Based on this, eight electromechanical hydraulic valves are actuated which determine the gear ratio of the transmission (gear selection), the working pressure and the torque converter lockup.

Transmission control function sequence

The function sequence for the transmission control is split up into the following points:

Basic shift program
Electronic and hydraulic transmission control function sequence
Kick-down function sequence
Limp-home mode function sequence

Basic shift program

The basic shift program includes upshift and downshift characteristics for all 7 gears, designed for:

Empty vehicle
Operating temperature
Level road
Sea level

The fully integrated transmission control unit (VGS) monitors and shifts depending on:

Vehicle speed
Selector lever position
Accelerator pedal position
Signals over the drive train CAN (CAN C)

Slow accelerator release:

Undesired downshifts in the upper vehicle speed range are prevented

Rapid accelerator release:

Upshifting to the next gear up is prevented and only permitted again when the vehicle accelerates slowly

Electronic and hydraulic transmission control function sequence

While the electronic transmission control takes over the gear selection and adaptation of pressures to the torque to be transmitted, the power supply of the transmission is controlled via the hydraulic elements of the electric controller unit (VGS). The oil supply to the hydraulic elements, such as the torque converter, the shift elements and the hydraulic transmission control, is provided by way of an oil pump connected to the torque converter. The transmission control system makes possible a precise adaptation of pressures to the respective operating conditions and to the engine output during the gearshift phase, resulting in a significant improvement in shift quality. It is possible to reach the engine RPM limit in the individual gears using full throttle and kickdown.

The transmission control system prevents impermissibly high engine speeds with a downshift lockout device. Furthermore, the transmission control system offers the advantage of a flexible adaptation to various vehicle and engine versions.

Kick-down function sequence

The driver's wish for maximum acceleration is met by the kickdown function.

The kickdown function is activated as of a pedal travel > 90 %. The "kick-down" signal is routed from the CDI control unit or ME-SFI [ME] control unit to the fully integrated transmission control unit via the drive CAN

Based on this information the fully integrated transmission control (VGS) control unit actuates the control solenoid valves so that the upshifts and downshifts take place at higher engine speeds in order to achieve maximum performance.

Limp-home mode function sequence

If the signals are implausible, the transmission control system is only partially operational and switches to the programmed emergency performance map.

The electronic selector lever module control unit enables the driver to select the required gear ranges "P, R, N, D".

The driver can choose been forward and reverse travel, engage the park pawl or interrupt the power flow between torque converter and transmission in the neutral position.

Component description for instrument cluster	A1	GF54.30-P-6000G
Component description for CDI control unit	N3/9 Model 463.303/340/341/306/336/346	GF07.16-P-6000GZ
Component description for ME-SFI [ME] control unit	N3/10 Model 463.202/222/236/237	GF07.61-P-6000G
Component description for electronic selector lever module control unit	N15/5	GF27.60-P-5163GGA
Component description for fully integrated transmission control unit	Y3/8n4	GF27.60-P-5165GGA