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

GF27.60-P-2000AHK Gear Shift, Function
- TRANSMISSION 722.904 /906 /907 /999 in MODEL 171.4 as of Model Year 09 /modification year 08 model refinement package

Function requirements for shift operation, general

^ Circuit 87 ON
^ Circuit 61 (engine running)
^ Engine speed from motor electronics control unit(N3/10)
^ Transmission not in limp-home mode
^ Engine compartment 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.

Taking into account various information, the electronic selector lever module control unit (N15/5) passes on selector lever positions "P, R, N, D" to the fully integrated transmission control unit (VGS).

The electronic selector lever module control unit changes the position of the selector range lever which is passed on mechanically to the selection range sensor (VGS) (Y3/8s1).

The shift range is displayed in the instrument cluster (A1).

The shift range can be changed in the forward gears while driving, but the fully integrated transmission control unit (VGS) prevents a shift at unacceptably high or low engine speeds.

Shift operation, function sequence

The function sequence is subdivided into the following steps:
^ Upshifting and downshifting
^ Shift operation 1 to 2

Upshifting and downshifting

In the transmission modes Sport "S" and Comfort "C" the driver can select the following functions by operating the selector lever (touch- mode (±)) or via the steering wheel gear shifter MINUS (S110/1) and steering wheel gear shifter PLUS (S111/1) (with code 428 Steering wheel shift paddles):

One press towards "-" activates the gear limitation or touchshift 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" compared with transmission mode Sport "S" a shorter shift range (shifting at low engine speed) and therefore a lower drive torque is available when starting off in forwards and reverse gear.

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 via the steering wheel gear shifter MINUS and PLUS (with code 428 Steering wheel shift paddles).

Reverse gear, park position and neutral can only be engaged via the electronic selector lever module control unit.

Manual transmission mode

Transmission mode Manual "M" is no longer active after ignition "OFF" -] "ON".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

Shift operation 1 to 2

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 motor electronics control unit (N3/10).

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.