GF27.60-P-2000AHC Gear Shift, Function
GF27.60-P-2000AHC Gear shift, function
- Transmission 722.902/904/906/908
Function requirements
^ Circuit 87 ON
^ Circuit 61 ON
^ Engine speed from CDI control unit (N3/9) (with diesel engines) or ME-SFI control unit (N3/10) (with gasoline engines)
^ Transmission not in limp-home mode
^ Signals from drive train CAN (CAN C)
General
The fully integrated transmission control controller unit (Y3/8) converts the electrical signals coming from the fully integrated transmission control unit (Y3/8n4) into hydraulic signals.
The electronic selector lever module control unit (N15/5) passes on selector lever positions "P", "R", "N" and "D" to the fully integrated transmission control unit taking into account various pieces of information.
The electronic selector lever module control unit changes the position of the selector range lever which is transmitted mechanically to the selection range sensor (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 prevents a shift operation if the engine speeds are too high or too low.
Function sequence
The function sequence is described in the following steps:
^ Function sequence for upshift and downshift
^ Function sequence of gearshift, gear 1 to 2
Function sequence for upshift and downshift
In transmission modes Sport "S" and Comfort "C" the driver can select the following functions by operating the selector lever (touch mode (±)) or downshift steering wheel gearshift button (S110/1) or upshift steering wheel gearshift button (S111/1):
One press towards "-" activates the gear limitation or touch shift 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" and "7" can be engaged directly via the downshift and upshift steering wheel gearshift buttons.
Reverse gear, park position and neutral can only be selected by way of the electronic selector lever module control unit.
The transmission mode Manual "M" (except code (494) USA version) is no longer active after status change circuit 15. The vehicle then always starts off in the transmission mode last selected ("S" or "C").
Function sequence of gearshift, gear 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 can be started by the fully integrated transmission control unit. 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 multidisk brake B1 being increased and, if necessary, by the CDI control unit (with diesel engines) or by the ME-SFI control unit (with gasoline engines) reducing engine torque.
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.
