GF27.60-13-2000LEH Gear Shift, Function

GF27.60-13-2000LEH Gear shift, function
- TRANSMISSION 722.950

Function requirements for shift operation, general
^ Circuit 87 (connected circuit 15) ON
^ Circuit 61 (engine running)
^ Motor speed from ME-SFI [ME] control unit (N3/10)
^ Vehicle speed
^ Transmission not in limp-home mode
^ Drive train CAN (CAN C) signals

Shift operation, general
The electric controller unit (VGS) (Y3/8) converts the electrical signals coming from the fully integrated transmission control unit (VGS) (Y3/8n4) into hydraulic signals. The selector lever positions "P, R, N, D" from the DIRECT SELECT gear selector switch (S16/13) are transferred to the chassis CAN (CAN E) by the steering column tube module (N80). The ME-SFI [ME] control unit conveys the selector lever position information on the drive train CAN.

Taking various information into account, the intelligent servo module for DIRECT SELECT (A80) transfers the selector lever positions to the fully integrated transmission control unit (VGS).

The intelligent servo module changes the position of the selector range lever, which is transmitted to the selection range sensor (VGS) (Y3/8s1).

The basic shift program can be influenced by the driver through the transmission mode button (A40/9s8).

The actuation of the transmission mode button is converted by the electronics of the front central operating unit (A40/9) into CAN messages and sent to the telematics CAN (CAN A). The COMAND control unit (A40/3) reads in these CAN messages and sends them as a signal to the central CAN (CAN-F). The signal is then sent over the central CAN with the interface of the central gateway control unit (N93), over the chassis CAN (CAN E) with the interface of the ME-SFI [ME] control unit to the fully integrated transmission control unit (VGS) (Y3/8n4).

The gear indicator (A1p12) and transmission mode display (A1p16) are shown in the instrument cluster (A1).

Shift operation, function sequence
The function sequence is described in the following steps:

^ Function sequence for shifting up and down
^ Function sequence for 1 to 2 shift

Function sequence for shifting up and down
In transmission modes Sport "S" and Comfort "C" the driver can select the following functions by operating the steering wheel gear shifter MINUS (S110/1) and the steering wheel gear shifter PLUS (S111/1):

One press toward "-" activates the gear limitation function (a downshift is made to the gear that lies exactly one below the currently selected one if the engine speed allows).

Pressing and holding towards "-" selects the "Shift to optimal gear" function (the gear which allows the best vehicle acceleration is selected).

One press toward "+" with the gear limitation function selected increases gearshift limitation by one gear (e.g. from 3 to 4).

One press toward "+" in gear range "D" sends an upshift request to the transmission (the transmission shifts up if the driving situation allows).

Pressing and holding toward "+" cancels the gear limitation function completely (gearshift to "D").

In transmission mode Comfort "C", in comparison to transmission mode Sport "S", a shorter shift range (shifting at low engine speed) and therefore a lower torque is available when starting off forwards and starting off in reverse.

This enables a gentler start-off as the gears are not driven to the limit.

In transmission mode Manual "M" (except code (494) USA version), the individual gears "1, 2, 3, 4, 5, 6, 7" can be shifted directly using the MINUS and PLUS steering wheel gear shifters.

Manual transmission mode
Transmission mode Manual "M" is no longer active after ignition "OFF" --> "ON". The vehicle then always starts off in the transmission mode last selected ("S" or "C").

Shift range
Although the shift range can be changed in the forward gears while driving, the fully integrated transmission control unit (VGS) prevents a shift operation if the engine speed is too high or too low.

Function sequence for 1 to 2 shift
Multidisk brake B2, multidisk brake B3 and multidisk clutch K3 are engaged in 1st gear. When shifting from 1st gear to 2nd gear, multidisk brake B3 is disengaged and multidisk brake B1 is engaged.

The shift operation is started by the fully integrated transmission control unit (VGS). Here, the multidisk brake B1 is filled and the pressure in multidisk brake B1 is increased continuously. Simultaneously the pressure in multi-disk brake B3 is reduced. This involves a flowing transition. When the 2nd gear torque is reached, the engine speed must be adapted to the 2nd gear level (elevation phase).

This speed adjustment is achieved by the pressure in the multi-disk brake B1 being increased and, if necessary, engine torque being reduced via the ME-SFI [ME] control unit

A forced downshift occurs at excessively low rpm and a forced upshift occurs at an excessively high rpm.

When the vehicle is stationary the transmission automatically shifts into 1st gear. It is possible to start off both in 1st or 2nd gear.