GF27.60-P-2000AHI Gear Shift, Function
GF27.60-P-2000AHI Gear shift, function
- TRANSMISSION 722.930
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
^ 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 ones.
Shift operation, function sequence
The function sequence is subdivided into the following steps:
^ Upshifting and downshifting
^ Shift operation 1 to 2
The electronic selector lever module control unit (N15/5) routes the selector lever positions "P, R, N, D" via the engine-compartment CAN to the fully integrated transmission-control control unit (VGS) taking different information into consideration.
The electronic selector lever module control unit changes the position of the selector range lever, which is transmitted mechanically to the selection range sensor (VGS) (Y3/8s1). The shift range is displayed in the instrument cluster (A1). 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.
Upshifting and downshifting
In the Sport "S", Sport Plus "S +" and Comfort "C" transmission modes the driver can select the following functions by pressing the selector lever (touch mode (±)) or the steering wheel gear shifter MINUS (S110/1) and the steering wheel gear shifter PLUS (S111/1):
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 comparison to transmission mode "S" and "S +" the Comfort C transmission mode has a shorter shift range (shifting at low engine speed) and therefore a lower drive torque when starting off in a forward or reverse direction.
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.
Reverse gear, park position and neutral can only be selected by way of the electronic selector lever module control unit.
Manual transmission modes
Transmission mode Manual "M" is no longer active after ignition "OFF --> "ON". The transmission always starts in the last selected transmission mode. ("S" "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.
