GF27.60-P-2000AHV Shift Operation, Function

GF27.60-P-2000AHV Shift Operation, Function
- TRANSMISSION 722.930 in MODEL 204.0 /2 /3

Function requirements for shift operation, general

^ Status "Circuit 87 ON"
^ Circuit 61 (engine running)
^ Engine speed, from ME-SFI [ME] control unit (N3/10)
^ Transmission not in limp-home mode
^ Chassis CAN (CAN E) signals

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 electronic selector lever module control unit (N15/5) forwards the selector lever positions "P", "R", "N" and "D" to the fully integrated transmission control unit over the drive train CAN (CAN-C) taking various pieces of information into account.

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 information is sent by the fully integrated transmission control unit over the drive train CAN to the ME-SFI [ME] control unit (N3/10) and on over the chassis CAN to the instrument cluster (A1). The engaged gear range is shown to the driver on the instrument cluster's multifunction display (A1p13).

The driver can shift up or down by operating the steering wheel gearshift buttons.

The status messages for the steering wheel upshift button (S111/1) or the steering wheel downshift button (S110/1) are read in by the steering wheel electronics (N135) and sent over the steering wheel LIN (LIN E1) to the steering column tube module control unit (N80).

The steering column tube module control unit routes the information over the chassis CAN to the ME-SFI [ME] control unit and forwarded over the drive train CAN to the fully integrated transmission control unit. This converts the shift requests into hydraulic signals, which are then sent to the respective solenoid control valves.

The shift into each gear step is conducted taking various input signals into consideration that are evaluated by the fully integrated transmission control unit.

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.

The gear step change is shown to the driver on the instrument cluster's gear indicator (A1p12). The fully integrated transmission control unit sends the status message over the drive train CAN to the ME-SFI [ME] control unit. The ME-SFI [ME] control unit sends the information over the chassis CAN to the instrument cluster, which actuates the gear indicator.

Function sequence for shift operation

The function sequence is subdivided into 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 the Sport ("S") and Sport Plus "S+" and Comfort "C" transmission modes, which can be set using the transmission mode rotary switch (S192), the driver can select the following functions using the steering wheel downshift button and the steering wheel upshift button:
- Pressing the steering wheel downshift button once activates the gear limitation function or triggers the downshift function which, if the engine speed permits, causes the transmission to shift down to the gear that is one gear below the gear currently engaged.
- The function "Shift into optimum gear" is selected by pressing and holding the downshift steering wheel gearshift button. The gear that allows optimum acceleration of the vehicle is selected
- Pressing the steering wheel upshift button once with gear limitation selected increases gearshift limitation by one gear (e.g. from 3rd gear to 4th gear).
- Pressing the steering wheel upshift button once with gear range "D" selected sends an upshift request to the fully integrated transmission control. The latter then shifts up according to the driving situation. Pressing and holding down the upshift steering wheel gearshift button cancels the gear limitation function completely (gearshift to "D").
- In comparison with 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 Manual ("M") transmission mode the individual gears "1", "2", "3", "4", "5", "6", "7" can be directly selected using the steering wheel downshift button and the steering wheel upshift button.
- 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" is no longer active if the status of circuit 15 changes. The transmission always starts in the last selected transmission mode. ("S", "S+" or "C").

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, upshift occurs at an excessively high rpm. When the vehicle is 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 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 multi-disk brake B1 being increased and, if necessary, engine torque being reduced via the ME-SFI [ME] control unit.

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.