Gear Shift, Function - GF27.60-D-2000TSA
Transmission 725.0 in model 907
Shift operation, function
The function sequence is described in the following steps:
- Shift operation, general
- Function sequence for shifting up and down
- Function sequence for 1 to 2 shift
Shift operation, general
To check the function requirements, the fully integrated transmission control unit (N15/15n4) reads in the following signals via drive CAN (CAN C):
- Circuit 15 ON from electronic ignition lock (EZS) control unit (N73/8) via the suspension FlexRay (Flex E) and powertrain control unit (N127)
- Running combustion engine from the ME-SFI control unit (N3/36)
- Motor rpm from the ME-SFI [ME] control unit
- Vehicle speed from instrument cluster (A1) via CAN HMI, electronic ignition lock (EZS) control unit, suspension FlexRay and powertrain control unit
The ME-SFI control unit transmits the status of the engine management to fully integrated transmission control unit via drive train CAN.
The ESP® control unit (N30/4) sends the signal for the operational drivetrain to the fully integrated transmission control unit via the suspension FlexRay, powertrain control unit and the drive CAN.
The fully integrated transmission control (VGS) electric controller unit (N15/15) converts the electrical signals issued by the fully integrated transmission control unit (N15/15n4) into hydraulic signals.
Gear ranges "R", "N", "D1" to "D9" and "P" can be engaged by operating the DIRECT SELECT lever (S16/13).
The DIRECT SELECT lever transmits information on the selected drive range "P", "R", "N", "D1" to "D9" via the steering column tube module (MRM) control unit (N80), which sends the signal to suspension FlexRay. The signal is registered by the powertrain control unit and sent via the drive train CAN to the fully integrated transmission control unit.
The shift range for engaged gear range "D1" to "D9" is shown on the instrument cluster.
Although the shift range can be changed in the forward gears while driving, the fully integrated transmission control unit prevents a shift operation if engine speeds are too high or too low
Information on the selected gear, drive range or drive program is forwarded by the fully integrated transmission control unit to the instrument cluster. This then actuates the relevant display via the following signals:
- Gear indicator, actuation
- Transmission mode display, actuation
The following component parts are actuated by the fully integrated transmission control unit:
- Park pawl lift solenoid (N15/15l1)
- Lubrication pressure solenoid (N15/15y12)
- Clutch control solenoid K81 (N15/15y13)
- Clutch control solenoid K38 (N15/15y14)
- Clutch control solenoid K27 (N15/15y15)
- Multidisk brake control solenoid B08 (N15/15y16)
- Multidisk brake control solenoid B05 (N15/15y17)
- Multidisk brake control solenoid B06 (N15/15y18)
- Working pressure solenoid (N15/15y19)
- Torque converter lockup clutch solenoid (N15/15y20)
The following signals are processed by the fully integrated transmission control unit:
- Pressure sensor (N15/15b5)
- Turbine wheel rpm sensor (N15/15n1)
- Internal input speed rpm sensor (N15/15n2)
- Output shaft rpm sensor (N15/15n3)
- Transmission oil temperature sensor (N15/15s2)
- Park pawl position sensor (N15/15s4)
Function sequence for shifting up and down
The drive ranges can be engaged by operating the DIRECT SELECT lever.
The fully integrated transmission control (VGS) electric controller unit converts electrical signals issued by the fully integrated transmission control unit into hydraulic signals.
The following transmission modes are available:
- "R" (Reverse gear)
- "N" (Idle)
- "P" (Park position with park pawl)
- D1 to "D9" (Drive ranges)
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. By pressing the steering wheel downshift button (S110/1) or the steering wheel upshift button (S111/1) the driver can select the following functions:
- The short-term M mode is activated by pressing the steering wheel gearshift buttons in the transmission modes. This allows the driver to change gear using the steering wheel gearshift buttons without having to select the short-term M mode beforehand. The previous "Gear limitation/shift to optimum gear" function, operated using the steering wheel gearshift buttons, has been discontinued.
- The short-term M mode is automatically deactivated again after a specific period. This time interval starts again after every additional press of a button. The activity of the function is extended depending on the wide open throttle and lateral acceleration involved.
- In the "M" (Manual) drive program, the individual gears "1" to "9" can be engaged directly using the steering wheel gearshift buttons.
The reverse gear and neutral position can only be engaged using the DIRECT SELECT selector lever. The park pawl (drive range "P") is activated using the DIRECT SELECT lever. Function sequence for 1 to 2 shift
Multidisk brake B05, multidisk brake B06 and multidisk clutch K38 are engaged in 1st gear. When shifting from 1st gear to 2nd gear, the B05 multidisk brake is disengaged and the K81 multiplate clutch is engaged.
The shift operation can be started by the fully integrated transmission control unit. The K81 multiplate clutch is filled and the pressure in the K81 multiplate clutch is continuously increased. Simultaneously the pressure in multidisk brake B06 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 raising the pressure in the multiplate clutch K81 and, if applicable, by the ME-SFI control unit performing a torque reduction.
A forced downshift occurs at excessively low rpm and a forced upshift occurs at an excessively high rpm. If the vehicle is stationary, 1 st gear is automatically selected. It is possible to start off both in 1st or 2nd gear.
| Overview of system components of automatic transmission (AT) | GF27.10-D-9992TSA |