Introduction - automatic transmission
- Make
- Alfa Romeo
- Model
- 159 Factory Service Manual
- Year
- 2005–2011
- Section
- General › Introduction - automatic transmission
INTRODUCTION - AUTOMATIC TRANSMISSION
GENERAL SPECIFICATIONS
- Type 6-speed automatic transmission
- Architecture: 3 clutches, 2 brakes, 1 free wheel, 2 epicyclic trains
- Hydraulic: 4 linear solenoids, 2 on/off solenoids
- Electronic: Neutral Start Switch and control unit built in, internal wiring and speed sensors
| NAME | AT6 | |||
|---|---|---|---|---|
| TRANSMISSION RATIO | 1 | 4.148 | ||
| 2 | 2.370 | |||
| 3 | 1.556 | |||
| 4 | 1.155 | |||
| 5 | 0.859 | |||
| 6 | 0.686 | |||
| R | 3.394 | |||
| Idler shaft | 0.836 | |||
| Differential | 3.188 | |||
| BRAKES AND CLUTCHES | CLUTCHES | C1 | 1 flange, 6 discs, 6 plates | 1 flange, 7 discs, 7 plates |
| C2 | 1 flange, 3 discs, 3 plates | 1 flange, 4 discs, 4 plates | ||
| C3 | 1 flange, 4 discs, 4 plates | |||
| BRAKES | B1 | Band | ||
| B2 | 2 flanges, 6 discs, 5 plates | 2 flanges, 6 discs, 5 plates | ||
| One-Way | F1 | Roller type | ||
| SOLENOIDS | Shift solenoid | n. 2 | ||
| Linear | n. 6 | |||
| LINE PRESSURE [KPa] | MINIMUM | D | 372 - 414 | |
| R | 575 - 665 | |||
| STALL | D | 1350 - 1460 | ||
| R | 1905 - 2125 | |||
FUNCTION
Neutral control
When the vehicle stops with the lever set to "D", the clutches are automatically released and the transmission changes to neutral. In this way, the torque converter is not put under stress, there are fewer vibrations and fuel consumption is minimal.
On rough roads or on hills, the function does not activate. On hills, the transmission remains engaged to assure a hill holder effect.
Reversing control
When the gear lever is shifted from "N" to "R", reverse is not engaged if vehicle speed exceeds 11 km/h.
Adaptivity
| MODE | DESCRIPTION |
|---|---|
| ADAPTIVITY | Used during normal driving The sports or economy modes are selected automatically depending on driving conditions |
| SPORT | In this mode, the speed passage points and lock-up operation are higher because the rpm is higher |
| WINTER/LOW GRIP | In the event of ice, snow and low grip in general, the car sets off in third gear to prevent the front wheels slipping |
| TIP | When the lever is moved from “D” to “+/-”, the driver can select the speed passage point sequentially. In any case, the control unit changes the ratio automatically to prevent over-revving or viceversa to prevent juddering because the engine speed is too low. |
| HIGH TEMPERATURE | If the transmission fluid temperature is too high, the control unit advances lock-up intervention to prevent the torque converter slipping excessively and thus lowering the temperature. |
| HEATING | Conversely, in this case converter slip is promoted to heat the fluid. |
| GRADIENTS | A gradient is automatically detected by a control unit algorithm based on rpm increase. The speed passage points are increased. |
| DESCENT | Conversely, on a descent, the system uses certain features to prevent excessive use of the brakes (lock-up etc.) |
| FAST ON | This control computes the driver''s desire for performance expressed by pressure on the accelerator pedal, and adjusts the speed passage points accordingly. |
| BRAKE ASSISTANCE | Conversely, in this case the engine brake is used to help the driver during acceleration (detected via the accelerator pedal) |
COMPONENTS
Control unit
The control unit is fitted on the speed engagement selector and assists the gearbox and gear control lever management functions.
PIN OUT
| 1 | Key switch signal |
| 2 | N.C. |
| 3 | N.C. |
| 4 | K line |
| 5 | Steering lock signal |
| 6 | CAN L |
| 7 | CAN H |
| 8 | CAN H |
| 9 | Earth |
| 10 | N.C. |
| 11 | Fuel system |
| 12 | N.C. |
| 13 | Reversing light relay |
| 14 | CAN L |
| 15 | N.C. |
| 16 | N.C. |
Input/output managed by the control unit
The interface with the automatic transmission system manages information by means of the following serial networks:
C-CAN (information, data)
Diagnostic line K
| SIGNAL | I/O | TRANSMISSION TYPE |
|---|---|---|
| key status | I | CAN |
| System warning light | O | CAN |
| Transmission fluid max temperature warning light | O | CAN |
| Speed engaged display | O | CAN |
| Gear selection | I | CAN |
| System diagnosis | I/O | K |
| Vehicle speed | I | CAN |
| Brake pedal pressed for recovery (brake light contact) | I | CAN |
| Driver''s front door status | I | CAN |
| Horn activation | O | CAN |
| Start-up enablement to NBS | O | on/off @GND |
| Reversing light control | O | on/off @+15 |
| Engine coolant temperature | I | CAN |
| Engine torque change request | O | CAN |
| MIL warning light activation request | O | CAN |
Wiring
The wiring is located inside the gearbox, it is connected to the inside of the valve body:
- to the speed sensors
- to the fluid temperature sensor
- to the solenoids
The wiring is connected to the transmission control unit with an Aisin pin-to-pin connector.
Solenoid unit
The valve unit, via solenoids activated by signals from the control unit, supplies hydraulic pressure produced by the oil pump to the brakes, clutches and lock-up. Part of the fluid is also sent to lubricate the mechanical components.
1. Control unit
2. Torque converter
3. Solenoid unit
4. Brakes/clutches
5. Oil radiator
6. Oil pump
7. Epicyclic gear set
Solenoids
The linear solenoids shown in the figure control the hydraulic pressure of almost all the brakes/clutches
ON/OFF solenoid: these 2 solenoids control brake "B2" for the engine brake in first gear
Linear solenoid SLT: controls line pressure linearly on the basis of a throttle signal and engine torque
Linear solenoid SLU: controls lock-up pressure linearly in relation to:
throttle signal
engine rpm
gearbox input speed
gearbox output speed
Sensors
Lever position sensor (nsw)
The position sensor is Hall effect and is built into the control unit. It sends the gear lever position.
1. Lever position sensor
2. Control unit
Fluid temperature sensor
The fluid temperature sensor is an NTC and is integral with the wiring.
1. Oil temperature sensor
Specifications:
| Temperature (°C) | Resistance (kΩ) |
|---|---|
| 10 | 5.62-7.31 |
| 25 | 3.5 |
| 110 | 0.22-0.27 |
Speed sensors
1. Output speed sensor
2. Input speed sensor
The input speed sensor detects the input speed to the gears, i.e. the converter turbine speed.
The output speed sensor detects the rotating speed of the gear that carries drive to the differential.
GEAR CONTROLS
The request to change gear may take place in the following ways:
- sequential (manual) or automatic via the selector lever
- sequential (manual) via the steering wheel controls (where present).
Selector lever
P = Park
R = Reverse
N = Neutral
D= Drive, automatic forward gear
+ = Shift from higher transmission ratio in sequential mode
- = Shift from lower transmission ratio in sequential mode
Manual sequential command from selector lever
The 6 gear changes can be managed sequentially by moving the lever to the right and raising it in the + direction engages a higher ratio whilst lowering it in the - direction engages a lower ratio.
Each gear engaged is shown by a number on the instrument panel display.
Automatic command from selector lever
The automatic command D can be selected from the sequential operation in any driving conditions.
The optimum ratio is selected by the gearbox electronic control unit depending on the engine speed and load conditions.
Manual sequential command from steering wheel (where present)
The change can be managed sequentially via the controls on the steering wheel.
To use the controls of the steering wheel, the gear lever must be in a (manual) sequential position:
- operating the lever on the steering wheel in the + direction engages a higher ratio
- operating the lever on the steering wheel in the +-direction engages a lower ratio
Automatic driving mode selection (where present)
It is possible to select different driving modes by pressing the SPORT/WINTER button on the gearbox control panel.
The following driving modes are available:
- NORMAL: gear changes at low engine speeds, favouring comfort and reduced consumption
- SPORT: gear changes at higher engine speeds, enhancing sporty driving
- WINTER: programme for setting off on roads in poor grip conditions.
The selection mode remains in force until the button is pressed again or the engine is switched off.
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