GF27.60-P-2000AHT Gear Shift, Function

GF27.60-P-2000AHT Gear Shift, Function
- TRANSMISSION 722.931 in MODEL 221.074 /174, 216.374

Function requirements for shift operation, general

^ Circuit 87 ON
^ Circuit 61 (engine running)
^ Motor speed from ME-SFI [ME] control unit (N3/10)
^ 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 gear selector switch 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 transmits the information to the drive train CAN. The intelligent servo module for DIRECT SELECT (A80) forwards the position of the selector range lever, taking various pieces of information into account, to the fully integrated transmission control unit (VGS).

The intelligent servo module for DIRECT SELECT changes the position of the selector range lever, which is recorded by the selection range sensor (VGS) (Y3/8s1).

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.

Display of selected gear range

The fully integrated transmission control unit (VGS) sends the information on the position of the selector range lever over the drive train CAN to the ME-SFI [ME] control unit and forwards it over the chassis CAN to the central gateway control unit (N93). The central gateway control unit then sends the position of the selector range lever to the instrument cluster (A1), which indicates the currently engaged gear range to the driver on the multifunction display (A1p13).

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) or 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" the individual gears "1, 2, 3, 4, 5, 6, 7" can be shifted directly using the MINUS and PLUS steering wheel gear shifter.

The reverse gear, park position and neutral position can only be engaged using the DIRECT SELECT gear selector switch.

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").

Display of selected transmission mode

The fully integrated transmission control unit (VGS) sends the status of the currently engaged transmission mode over the drive train CAN to the ME-SFI [ME] control unit and then forwards it over the chassis CAN to the central gateway control unit. This then sends the information over the central CAN (CAN F) to the instrument cluster.

The selected transmission mode is indicated to the driver on the transmission mode display (A1p16) in the instrument cluster.

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.

A forced downshift occurs at excessively low rpm and a forced

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

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.

Display of engaged gear stage

The fully integrated transmission control unit (VGS) sends the status of the currently engaged gear stage over the drive train CAN to the ME-SFI [ME] control unit. The ME-SFI [ME] control unit routes the information over the chassis CAN to the central gateway control unit and forwards it over the central CAN to the instrument cluster

The shifting range is shown to the driver on the gear indicator (A1p12) in the instrument cluster.