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

TRANSMISSION 722.9 (except 722.930) in MODEL 205 

Function requirements for shift operation, general 

Shift operation, 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 selector lever positions "P", "R", "N", "D" of the DIRECT SELECT lever (S16/13) are transmitted via the steering column tube module control unit (N80) on the chassis FlexRay (Flex E) to the powertrain control unit (N127). This forwards the information via drive train CAN to the intelligent servo module for DIRECT SELECT (A80) and the fully integrated transmission control unit.

The intelligent servo module for DIRECT SELECT changes the position of the selection range lever, which is forwarded mechanically to the selection range sensor (Y3/8s1).

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.

IMPORTANT Messages and displays in instrument cluster (A1)

Information relative to the selected gear, gear range or the transmission mode are sent by the fully integrated transmission control unit to the drive train CAN. The powertrain control unit receives and relays them via the chassis FlexRay and the user interface CAN (CAN HMI) with the interface of the electronic ignition lock control unit (N73) to the instrument cluster. The engaged gear range is displayed to the driver via the multifunction display (A1p13) in the instrument cluster. The gear step change is shown to the driver on the instrument cluster's gear indicator (A1p12). The transmission mode display (A1p16) is also shown to the driver in the instrument cluster.

Function sequence for shift operation 

The function sequence is described in the following steps:

Function sequence for gear limitation and shifting into optimum gear 

By pressing the steering wheel downshift button (S110/1) or the steering wheel upshift button (S111/1) the driver can select the following functions:

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 direction "+" in gear range "D" sends an upshift request to the transmission (the transmission shifts up depending on the driving situation).

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

Depending on the transmission mode selected, different long and short gear ranges are available (shifting at low or high engine speed) as well as the operating condition of adapted drive torques when starting off driving forward and backward.

The reverse gear, park position and neutral can only be shifted to using the intelligent servo module for DIRECT SELECT.

Function sequence for shifting up and down 

In transmission mode Economy "E", a shorter shift range (shifting at low engine speed) and therefore a lower drive torque are available for starting off forwards and in reverse in comparison to Sport ("S") transmission mode or Sport Plus "S+" for code 489 (Airmatic). This enables a gentler start-off as the gears are not driven to the limit.

IMPORTANT Display of selected transmission mode

The fully integrated transmission control unit sends the transmission mode status via drive train CAN to the powertrain control unit and onward via periphery CAN (CAN PER) with the electronic ignition lock control unit interface and via user interface CAN to the instrument cluster.

The selected transmission mode is indicated to the driver via the transmission mode display symbol in the instrument cluster.

Function sequence of gearshift 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. In the process the multidisk brake B1 is filled with oil and the pressure in the multidisk brake B1 is continuously increased. Simultaneously the pressure in multidisk 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, engine torque being reduced via the CDI control unit or ME-SFI control unit.

IMPORTANT

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.

IMPORTANT Display of engaged gear stage

The fully integrated transmission control unit sends the status of the currently engaged gear range via drive train CAN to the powertrain control unit and onward via periphery CAN with the electronic ignition lock control unit interface and via user interface CAN to the instrument cluster.

The engaged gear range is indicated to the driver via the gear indicator symbol in the instrument cluster.

IMPORTANT Short-term M program

The short-term M program is a temporary program that is activated when the steering wheel gearshift buttons or the DIRECT SELECT lever are operated. Pressing in the positive (+) direction triggers an upshift and pressing in the negative (-) direction triggers a downshift, insofar as this is permissible. If not, the current gear is maintained. After a specified time window, this function deactivates again automatically. The activated time can be extended by dropping below a minimum speed (e.g. stopping), when lateral acceleration is detected or when the vehicle is in a deceleration phase. If none of the stated criteria are active anymore, the M mode remains active for a prescribed remaining time. After this remaining time expires, the initial shift mode is returned to. In addition, the driver is shown a recommended shift operation in the instrument cluster. This is part of the gearshift recommendation that is also integrated. The driver can prematurely cancel the short-term M program through specific actions, e.g. if he/she operates and holds the upshift steering wheel gearshift button or the DIRECT SELECT lever in the "positive" direction, changes the gear range or changes the transmission mode. If one of these preconditions is met, a switch is made back to the initial shift program.

  Electrical function schematic for shift operation   PE27.19-P-2057-97FBA
  Torque converter lockup clutch control, function   GF27.20-P-3002AHE 
  Engage gear range, function   GF27.60-P-3009AHE 
  Emergency default mode, function   GF27.60-P-3012AHE 
  Control valve pressure, function   GF27.60-P-3017AHE 
  Torque converter lockup clutch control pressure, function   GF27.60-P-3019AHE 
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