939005762 - 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
	BRAKES	B2	2 flanges, 6 discs, 5 plates	2 flanges, 6 discs, 5 plates
	One-Way	F1	Roller type
SOLENOIDS	Shift solenoid		n. 2
SOLENOIDS	Linear		n. 6
LINE PRESSURE [KPa]	MINIMUM	D	372 - 414
	MINIMUM	R	575 - 665
	STALL	D	1350 - 1460
	STALL	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 unitThe 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 solenoidsThe 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 unit2. Torque converter3. Solenoid unit4. Brakes/clutches5. Oil radiator6. Oil pump7. 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 signalengine rpmgearbox input speedgearbox 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 sensor2. Control unitFluid temperature sensorThe fluid temperature sensor is an NTC and is integral with the wiring.

1. Oil temperature sensorSpecifications:

Temperature (°C)	Resistance (kΩ)
10	5.62-7.31
25	3.5
110	0.22-0.27

Speed sensors

1. Output speed sensor2. Input speed sensorThe 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 = ParkR = ReverseN = NeutralD= Drive, automatic forward gear+ = Shift from higher transmission ratio in sequential mode- = Shift from lower transmission ratio in sequential modeManual sequential command from selector leverThe 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 leverThe 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 ratioAutomatic 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.