6-Speed Automatic Transmission

24 01 05 (106)
6-speed automatic transmission
R52, R53, R56





Introduction
The 6-speed automatic transmission GA6F21WA (manufactured by AISIN LTD, Japan) will first be introduced on the MINI COOPER S and MINI COOPER S Convertible (from 01/05).

The 6-speed automatic transmission can be operated either manually with the Steptronic (manual mode) or the gearshift paddles on the steering wheel.
The gearshift mechanism is mechanically connected to the transmission via a selector lever cable.
> - R52, R53 [system overview ...]
> - R56 [system overview ...]
> - R52, R53, R56: Overview of components [system overview ...]

New features:
In drive position "D", it is possible to select an individual gear using the gearshift paddles on the steering wheel. The driver can change gear manually in drive position "D" without first having to move the selector lever to manual mode (Steptronic).
The automatic transmission is optional (option 205).

Brief description of components
The automatic transmission consists of the following components:

- EGS control unit
The automatic transmission is controlled by the EGS control unit (EGS stands for electronic transmission control).
The EGS control unit directly actuates the solenoid valves and the electronic pressure control valves.
Data is exchanged through the PT-CAN with the following control units:
- DME/DDE
- DSC
- JBE (R56 only)
- Auxiliary instrument (KOMBI2, R56)
- Instrument cluster (KOMBI; R52, R53)

- Hydraulic selector unit
The hydraulic selector unit controls the oil pressure in the drive and brake clutches in the automatic transmission.

- Selector lever, drive positions and selector lever position displays
The selector lever has the positions
p - for Park
R - for Reverse
N - for Neutral
D - for Drive (= automatic mode)
M/S - "M" for manual mode = Steptronic
"S" for Sport program = automatic mode with sporty map
The selector lever position display is located in the selector lever trim.
> R52, R53
> R56
- SPORT button
> R56
Activating the SPORT button affects the following functions:
- The transmission switches to the sporty map and the gearshift times are shortened
- The engine responds more directly to movements of the accelerator pedal.
- The steering responds more directly
The sporty shift program is activated as soon as the SPORT button is pressed. The system switches to the sporty shift program at less than 5 % and more than 95 % accelerator pedal movement
- Gearshift paddles
There are 2 gearshift paddles on the steering wheel that logically have the same functions:
- Upshift - pull briefly
- Downshift - press briefly
In automatic mode (drive position "D"), it is possible to change directly to manual mode. If within a certain period of time (R52, R53: approx. 6 seconds; R56: approx. 8 seconds, no gearshift is made and the vehicle does not accelerate significantly, the automatic transmission will change back to automatic mode.

- Automatic transmission range switch
The automatic transmission range switch is connected to the selector lever by a Bowden cable.
The automatic transmission range switch mechanically shifts the gear selector valve in the hydraulic selector unit. At the same time, the automatic transmission range switch uses sliding contacts to convert the mechanical motion of the selector lever into electrical signals.
The automatic transmission range switch delivers the selector lever position signals for the transmission control and for the display in the instrument cluster to the EGS control unit.
The automatic transmission range switch is installed on the transmission.
> R52, R53
The automatic transmission range switch directly actuates the reversing light.
> R56
The footwell module (FRM) actuates the reversing light.
- Display in the instrument cluster or auxiliary instrument
> R52, R53
Display in the instrument cluster (KOMBI)
> R56
Display in the auxiliary instrument (KOMBI2)
The drive range and drive program are displayed in the instrument cluster or auxiliary instrument, the signal required for this is sent from the electronic transmission control (EGS).
P: - for Park
R: - for Reverse
N: - for Neutral
D: - for Drive (= automatic mode)
> - R52, R53
SD: - when the selector lever is moved from position "D" into the "M/S" shift gate
> - R56
DS: - when the selector lever is moved from position "D" into the "M/S" shift gate
or
when the SPORT button is pressed
M1 ... M6: - for manual mode (Steptronic) using the gearshift paddles or the selector lever
EP: - indicates a malfunction in the automatic transmission (EP = Emergency Program)
- Torque converter with converter lockup clutch
The torque of the engine is transmitted to the automatic transmission in 2 ways:
1. Hydraulically via the torque converter
The torque converter transmits the torque from the engine to the transmission as follows: High engine speeds and low engine torque are converted into low speeds and high torque.
2. Mechanically via the converter lockup clutch
When the converter lockup clutch is closed, the impeller and turbine wheel are non-positively linked without the influence of friction. This prevents power loss within the torque converter and optimizes fuel consumption.
The converter lockup clutch creates a mechanical link between the output shaft of the engine and the input shaft of the transmission. The opening and closing of the converter lockup clutch is possible in 2nd to 6th gear. The converter lockup clutch is not closed at transmission oil temperatures less than 20 °C.
- Oil pump
The oil pump in the automatic transmission generates the necessary hydraulic pressure.
- Transmission oil cooler
The transmission oil cooler is installed on the transmission housing. The transmission oil cooler is connected to the engine cooling circuit. This ensures that the automatic transmission fluid is warmed up more quickly during the time taken for the engine to reach operating temperature. When the engine is at its normal operating temperature, the automatic transmission fluid is cooled by the engine cooling circuit.
- Multi-plate clutches
The automatic transmission requires 5 multi-plate clutches to shift between the 6 gears: 3 input clutches and 2 brake clutches.
- Lepelletier planetary gear set
The automatic transmission is equipped with a Lepelletier planetary gear set. A Lepelletier planetary gear set is a Ravigneaux set (double planetary gear set) with a preceding planetary gear.
The following control units and components are incorporated in the automatic transmission functions:
- Brake light switch
The signal from the brake light switch is needed for the function of the selector lever lock and the adaptive transmission control.
Signal path: Brake light switch -> DME/DDE -> PT-CAN -> EGS control unit
- Accelerator pedal module
The signal from the accelerator pedal module is needed for the adaptive transmission control.
Signal path: Accelerator pedal module -> DME/DDE -> PT-CAN -> EGS control unit
- DSC: Dynamic Stability Control
The Dynamic Stability Control optimizes driving stability when starting and accelerating, and optimizes traction. Within the limitations of the laws of physics, DSC compensates for driving conditions such as over/understeering. To do this, the DSC control unit is sent signals about the driving dynamics (e.g. wheel speed, lateral acceleration).
The DSC transmits the processed signals concerning cornering and acceleration identification to the EGS control unit.
The combination of front-wheel drive and DSC control eliminates the need for a special winter program in the electronic transmission control.
- DME or DDE: Digital engine electronics or digital diesel electronics
To actuate the transmission, the engine control unit (DME or DDE control unit) sends information about the engine's current operating status (e.g. engine speed or torque) to the electronic transmission control.
The electronic transmission control (EGS) reports the current operating status of the transmission back to the engine control unit.
- FRM: Footwell module
> R56
The reversing light is actuated by the FRM.
The transmission position switch supplies the signal concerning the selector lever position to the EGS control unit. The EGS control unit evaluates these signals. If the EGS control unit detects that the selector lever position "R" is engaged, the EGS control unit transmits a message to the footwell module (FRM).
- JBE: Junction box electronics
> R56
The JBE is the data interface (= gateway) between the K-CAN and PT-CAN (K-CAN stands for body CAN, PT-CAN stands for powertrain CAN).
The junction box consists of the JBE and the power distributor.
Amongst other things, the power distributor supplies the shift gate pattern and the ESG control unit.
- CAS: Car access system
> R56
The CAS controls the access options to the vehicle. The CAS control unit is the interface to the START-STOP unit with the holder for the remote control. When the CAS detects an authorized remote control, terminal R is switched on. At the same time, the remote control is locked in the holder. The locked remote control is a condition for the terminals to be switched (terminal R, terminal 15 with engine ON/OFF)
The engine start is initiated when the START/STOP button is pressed. If all preconditions are met (e.g. selector lever in position "P" or "N"), the engine start is enabled by the CAS.
In conjunction with Comfort Access (not necessary to insert the remote control in its holder), the engine can only be switched off when the selector lever is in position "P" (parking lock engaged).

System functions
The following system functions are described for the automatic transmission:

- Adaptive transmission control
- Uphill detection
- Downhill detection
- Kickdown
- Suppression of automatic upshifts if the throttle is closed quickly
- Cornering detection
- Overlap control
- Starter inhibitor
- Parking lock
- Engine intervention
- Downshift inhibitor
- Reverse gear inhibitor
- Selector lever lock (shiftlock)
- Interlock
- Overheating protection
- Emergency program



Adaptive transmission control
As with earlier automatic transmissions, the 6-speed automatic transmission offers the choice between a comfort program and 2 sport programs.
The adaptive transmission control (component of electronic transmission control) adapts the shift characteristics of the comfort program and sport programs to the driver's wish and the driving situation.
- Comfort program in selector lever position "D"
The comfort program allows comfortable automatic shift characteristics.
- Sport program in selector lever position "M/S"
> R52, R53 - Display "SD" in the instrument cluster
> R56: Display "DS" in the auxiliary instrument
The sport program allows dynamic, sporty shift characteristics. Gearshift are effected automatically.
- The sport program is activated via the SPORT button (R56 only)
The sport program allows very sporty gearshift characteristics compared to the sport program when the selector lever is in position "M/S".



Uphill detection
These functions are based on a comparison of actual car acceleration with a nominal value. From the current engine operating situation, the acceleration with normal load on a level surface is calculated. If the actual acceleration is significantly below the theoretical value, the "Driving uphill" function is activated.
The design of the corresponding shift characteristics allows a high-speed driving style. Undesirable upshifts and frequent up/downshifts are eliminated or greatly reduced.



Downhill detection
If the EGS control unit detects downhill driving, it will automatically shift down a gear if the vehicle's speed picks up. This enhances the engine's braking effect. A downshift is only made if the engine speed after the downshift will still be below the maximum speed allowed in the next gear down.
The EGS control unit recognizes driving downhill from the following signals:
- Throttle valve potentiometer (load)
- Wheel-speed sensors (roadspeed)
- Brake light switch (braking).



Kickdown
The driver's wishes are recorded using the pedal position transmitter potentiometer in the accelerator pedal module. When the accelerator pedal is fully depressed (kickdown pressure point exceeded), a signal is transmitted from the kickdown switch to the engine control unit. A CAN message shifts the automatic transmission to the lowest gear possible.



Suppression of automatic upshifts if the throttle is closed quickly
To decelerate the vehicle, the foot is taken off the gas and the brake depressed as necessary. The gearshift map triggers an upshift when the throttle is closed. These gearshifts are not necessary in conjunction with brake applications as they prevent the engine's braking effect from being exploited.
The intention to apply the brakes can often be anticipated from the accelerator pedal being rapidly released to the zero position. If such an action is detected, the upshift is suppressed for as long as the accelerator pedal is in the zero position and the vehicle is in overrun mode.



Cornering detection
Cornering detection reacts to the vehicle's lateral acceleration with an indirect adaptation to the driver type.
Lateral acceleration is considered an indirect statement of the preferred driving dynamics and does not cause an immediate gearshift response (shifts when cornering could adversely affect driving stability).
Lateral acceleration is calculated from the signals from the wheel-speed sensors, from the yaw rate and road speed.



Overlap control
Overlap control provides gentle shift characteristics as follows: With overlap control, several multi-plate clutches are in use at the same time. Here, pressure is reduced in the active multi-plate clutch and at the same time built up in the multi-plate clutch that is about to be activated. The reduction and build-up of pressure is maintained until a synchronized speed is reached. At this point, the hydraulic pressure for the multi-plate clutch to be activated can be built up completely. Overlap control is active for all gearshifts from 2nd to 6th gear and from 6th to 2nd gear.
A freewheel control is used for gearshifts into 1st gear. The freewheel links certain components of the Lepelletier planetary gear set in one direction of rotation.



Starter inhibitor
It is only possible to start the engine when the selector lever is in position "P" or "N".
The electronic immobilizer (EWS) evaluates the following signals from the automatic transmission range switch for the engine start:
- Selector lever position "P" or "N" as signal via the direct wire
> R56
The Car Access System (CAS) evaluates the signals from the transmission position switch for the start.



Parking lock
The parking lock (selector lever position "P") blocks the transmission output shaft. The vehicle is prevented from rolling unexpectedly. When the vehicle is stationary, the parking lock is engaged purely mechanically via the selector lever (Bowden cable from selector lever to automatic transmission range switch). The parking lock is designed to provide a reliable brake on gradients up to 32 %.



Engine intervention
During the gearshift, the EGS control unit emits signals to influence the DME/DDE (digital engine electronics / digital diesel electronics). The DME/DDE then retards the ignition timing for a few milliseconds.
This action briefly reduces the torque, improves shift quality, reduces the load on the transmission and shortens the shifting time.



Downshift inhibitor
The gearshift lock only allows a downshift if the engine speed after the downshift will still be below the maximum speed allowed in the next gear down. The engine speed signal is transmitted by the engine control unit to the EGS control unit.
The downshift inhibitor prevents damage to the engine and transmission.



Reverse gear inhibitor
The reverse gear inhibitor electronically prevents reverse gear from being engaged when the vehicle is moving (forwards) at speeds over 7 km/h. If the specified speed is exceeded, the necessary solenoid valve are not actuated.



Selector lever lock (shiftlock)
The selector lever is locked in positions "P" and "N" (by an electromagnet and a locking catch). The selector lever lock is controlled by the ESG control unit. The selector lever lock is engaged when selector lever position "P" or "N" is detected and the ignition (terminal 15) is ON.



Interlock
> R52, R53
The ignition lock is mechanically linked to the selector lever by a Bowden cable. The interlock only allows the ignition key to be removed when the selector lever is in position P. Conversely, the selector lever can only be moved from position "P" when the ignition key is in the ignition lock and turned at least to ignition ON.

> R56
When terminal 15 is OFF, the selector lever is locked in position "P" (by an electromagnet and locking catch). When the remote control is not in its holder, the selector lever is locked in position "P".
When terminal 15 is activated, the EGS control unit applies current to the electromagnet and the selector lever is released. A microswitch registers the locking or unlocking of the selector lever. The microswitch transmits a signal to the CAS (Car Access System) to enable the remote control.
- Interlock without convenience access
The remote control cannot be removed from its holder when the selector lever is not engaged in position "P". The selector lever is locked when the selector lever is in position P and the ignition is OFF. The remote control can be removed.
- Interlock with convenience access
The engine and terminal 15 (ignition) can only be switched off when the selector lever is in position "P".



Overheating protection
> R56
The maximum permissible constant operating temperature of the automatic transmission fluid in the oil sump is 125 °C.
If the oil sump temperature exceeds this value in drive positions "D" and "S", a 2-stage overheating protection set in as follows:
- Level 1: Automatic upshift from 5th gear to 6th gear
The transmission automatically shift up if the oil sump temperature exceeds 128 °C.
Overheating protection is deactivated when the oil sump temperature drops back below 123 °C.
- Level 2: Reduced engine output
If the oil sump temperature continues to rise in level 1 and reaches 132 °C, the engine's power output will be reduced by 20 %.
Overheating protection is deactivated when the oil sump temperature drops back below 123 °C.
If the oil sump temperature exceeds 150 °C, the EGS control unit will emit a Check-Control message and the Check-Control symbol for transmission temperature will light up (yellow).
In the conditions described, the overheating protection functions will lead to a drop in top speed and reduced acceleration.



Emergency program
The emergency program is activated if the transmission management should fail or detect a malfunction that could lead to critical driving conditions. In the emergency program, the vehicle remains operational, albeit with limitations.
If the electronic transmission control fails (without current), the following forward gears can be engaged:
Failure in 1st-3rd gear -> emergency 3rd gear
Failure in 4th-6th gear -> the current gear is maintained
3rd gear will be engaged after a restart.

Operation
The different automatic transmission drive positions are selected with the selector lever.
When driving, there are the following possibilities:

- D = Automatic mode
When the selector lever is in position "D", gears are selected by the adaptive transmission control.
- Gearshift using gearshift paddles
If the selector lever is in position "D" and a gearshift is initiated using the gearshift paddles, the automatic transmission will automatically change to manual mode.
If no gearshift is made and the vehicle does not accelerate significantly within 6 seconds, the automatic transmission will change back to automatic mode.

- SD = Automatic mode, sport program
When the selector lever is moved from position "D" into the shift gate "M/S", the automatic transmission's sport-shift program is activated.
The display in the instrument cluster changes from "D" to "SD".
> R52, R53
Move the selector lever from position "D" to the right to the "M/S" shift gate
> R56
Move the selector lever from position "D" to the left to the "M/S" shift gate
- M1 to M6 = Steptronic
If the selector lever is in shift gate "M/S" and is briefly moved to "-" or "+", the electronic circuitry changes to Steptronic. Permanent manual mode is activated with the selector lever or gearshift paddles. The display in the instrument cluster changes from "SD" to "M1" to "M6".
In manual (Steptronic) mode, the transmission management will only execute upshifts or downshifts at appropriate engine and road speeds. Gearshifts that would result in an excessively high or low engine speed are suppressed.

SPORT button
> R56
Press the SPORT button to select a sports program with very sporty gearshift characteristics.

Notes for service staff
Service staff should note the following points:

- Service notes:
- Diagnosis: ---
- Encoding/programming: ---
- Car and Key Memory: ---

Subject to change.