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

GF27.60-P-2000ACS Gear shift, function
- Transmission 722.649

Function requirements for shift operation, general
^ Circuit 87 ON
^ Circuit 61 (engine running)
^ Engine speed from CDI control unit (N3/9) or ME-SFI [ME] control unit (N3/10)
^ Transmission not in limp-home mode
^ Drive train CAN (CAN C) signals

Shift operation, general
The electric controller unit (Y3/6) converts the electrical signals coming from the ETC control unit (N15/3) into hydraulic signals. The selector lever positions "P, R, N, D" from the DIRECT SELECT gear selector switch (S16/13) are transferred to the chassis CAN (CAN E) by the steering column tube module (N80).

The CDI control unit or ME-SFI [ME] control unit transfers the information to the drive train CAN. Taking various information into account, the intelligent servo module for DIRECT SELECT (A80) forwards the selector lever positions to the ETC [EGS] control unit. The intelligent servo module changes the position of the selector range lever.

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

The shift range can be changed in the forward gears while driving, but the ETC control unit prevents a shift at unacceptably high or low engine speeds.

Shift operation, function sequence
The function sequence is subdivided into the following steps:
^ Function sequence for upshift and downshift
^ Shift to 1st gear, function sequence
^ Shift phase, function sequence
^ Shift to 2nd gear, function sequence

Function sequence for upshift and downshift
In the Sport "S" and Comfort "C" transmission modes, the driver can select the following functions by actuating the MINUS steering wheel gear shifter (S110/1) and the PLUS steering wheel gear shifter (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 with the transmission mode Sport "S" a shorter shift range (shifting at low engine speed) and therefore a lower drive torque is available. This enables a gentler start-off as the gears are not driven to the limit.

With transmission mode Manual "M" (except code (494) USA version) the individual gears "1, 2, 3, 4, 5" can be shifted directly via the steering wheel gear shifter MINUS and PLUS. Reverse gear, park position and neutral can only be selected by way of 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 to 1st gear, function sequence
The end face of the 1 - 2 or 4 - 5 command valve is kept depressurized via the 1-2 and 4-5 shift solenoid valve. Working pressure is applied via the 1 - 2 or 4 - 5 holding pressure shift valve to the multidisk brake B1 The multidisk clutch K1 is unpressurized.

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. possible due to the lack of excess force limitation.

Component Identification:

Shift phase, function sequence
Via the 1-2 and 4-5 shift solenoid valve, the shift valve pressure (p-SV) is switched so that it acts on the end face of the command valve 1 - 2 or 4 - 5 (31a). As a result, the command valve 1 - 2 or 4 - 5 (31a) is moved and the shift pressure (p-S) coming from shift pressure shift valve 1 - 2 or 4 - 5 (29a) is directed to the multidisk clutch K1 (24) via the command valve 1 - 2 or 4 - 5 (31a). At the same time, the multi-disk brake B1 (21) is subjected to overlap pressure from the overlap regulating valve 1 - 2 or 4 - 5 (30a).

The pressure acting at the face of shift pressure shift valve 1 - 2 or 4 - 5 (29a) from multidisk brake B1 (21) is relieved by working pressure (p-A). The increasing shift pressure (p-S) at the multi-disk clutch K1 (24) acts on the annular surface of the overlap regulating valve 1 - 2 or 4 - 5 (30a) and reduces the overlap pressure regulated by the overlap regulating valve 1 - 2 or 4 - 5 (30a). With an appropriate pressure level at the 1 - 2 or 4 - 5 holding pressure shift valve (28a) this valve switches over.

Component Identification:

Shift to 2nd gear, function sequence
After a successful gear-shift operation, the pressure at the end face of the command valve 1 - 2 or 4 - 5 (31a) is reduced via the shift solenoid valve 1-2 and 4-5 and the command valve is moved to its basic position. The working pressure (p-A) is routed via holding pressure shift valve 1 - 2 or 4 - 5 (28a) and command valve 1 - 2 or 4 - 5 (31a) to the multidisk clutch K1 (24).

The multi-disk brake B1 (21) is disengaged (unpressurized). The spring in shift pressure shift valve 1 - 2 or 4 - 5 (29a) pushes this to its basic position.