Description Part 3

The unit is located under the vehicle and is mounted on the cross-member, behind the transmission. The unit is identical for all engine derivatives.

The transfer box receives a torque input from the transmission output shaft, which is passed through the unit to two outputs for the front and rear drive shafts.

The input torque is equally distributed via a bevel gear type differential. In order to provide an optimal torque distribution to each wheel in all driving conditions, the unit is equipped with an electronically controlled locking and torque-biasing device. This device detects wheel slip via various vehicle system inputs to the transfer box control module and locks the differential accordingly. The locking torque is applied through a multiplate clutch assembly.

A planetary gear set, located in the differential assembly, allows the driver to select high or low range while driving. This is known as 'shift on the move'. When in low range, the planetary gear set provides a ratio of 2.93:1, which gives the vehicle an extremely low crawl speed for off road driving and trailer towing. High range is a direct drive from the transmission output shaft and provides a 1:1 ratio.

Both the center differential locking and biasing and the 'shift on the move' features are actuated via a DC transfer box motor, which is controlled via PWM signal by the transfer box control module.

COMPONENT LOCATION





NOTE: Manual transmission shown











TRANSFER BOX EXPLODED VIEW








TRANSFER BOX SECTIONAL VIEW

TRANSFER BOX POWER FLOW





Input torque from the transmission is transferred to the input shaft of the transfer box and then to the planetary sun gear and planetary pinion gears. The planetary pinion gears are held in place by the planet pinion shafts, which are connected to the differential carrier, and drive the differential pinion gears. The torque is then distributed to both the front and rear carriers, which are connected to the outputs of the transfer box. The rear carrier is connected directly to the rear output flange; the front carrier is connected to the sprocket and therefore to the chain drive, which provides the front output flange rotation.

SYSTEM OPERATION
High range is the default and is used for all normal road driving and for off-road driving across dry, level terrain. Low range should be used where low speed maneuvering is necessary, as in when negotiating steep slippery surfaces or boulder-strewn terrain or reversing a trailer. Low range should also be used for extreme off-road conditions where progress in high range cannot be maintained. Low range should never be used for normal road driving.

High or low range is selected using the range change selection switch in the center console. The driver requests a high-to-low range change by pushing the range change lever towards the rear of the vehicle and, conversely, a low-to-high request by pushing the lever towards the front of the vehicle. The range change lever is center-sprung and does not latch in the forward or rear positions.
Range change can be effected whether the vehicle is moving ('shift on the move') or stationary-, however, vehicle speed must be within preset parameters for the requested range and the transmission selector lever must be shifted into the neutral (W) position.
^ If a range change is requested when vehicle speed exceeds the preset limit, a 'SPEED TOO HIGH FOR RANGE CHANGE' message will be displayed in the message center and the request will be suspended until vehicle speed is reduced. Once vehicle speed is within limits, the message will extinguish and range change will proceed.
^ If a range change is requested and the transmission selector lever is in a position other than neutral, the request will be denied and a 'SELECT NEUTRAL FOR RANGE CHANGE' message will be displayed. If a range change is requested when transmission selector lever is in the 'P' position, the request will be denied, but the 'SELECT NEUTRAL' message will not be displayed. Once the selector lever is shifted to 'N', the message will extinguish and range change will proceed.
The accelerator pedal must not be depressed when a range change is in progress.

During range change the main transmission will be locked in neutral. The range change process can take up to one second to complete following an accepted request. Once range change is complete, the selector lever may be shifted out of 'N'.

The vehicle will remain in the selected range unless a change is manually requested-, it will not automatically revert to high range following a key off/key on sequence.

High-to-Low Range Change
A request for low range should not be made when vehicle speed exceeds 25 mph (40 km/h).

When low range is selected, the low range indicator status indicator will flash while the range changes and a 'LOW RANGE' message will display for approximately 3 seconds, followed by a chime to confirm that range change is complete. The status indicator will remain illuminated continuously while the vehicle is in low range. Only 'D' and 'Manual (Command Shift) mode' are available-, 'Sport mode' cannot be used in low range.

Low-to-High Range Change
A request for high range should not be made when vehicle speed exceeds 37 mph (60 km/h).

When high range is selected, the low range indicator status indicator will flash while the range changes and a 'HIGH RANGE' message will display for approximately 3 seconds, followed by a chime to confirm that range change is complete. The status indicator does not remain illuminated while the vehicle is in high range.

TRANSFER BOX CASINGS
The front and rear casing assemblies are manufactured from cast aluminum.

Front Casing Assembly
The front casing assembly provides the location for the input shaft bearing and the front output flange bearing. It is also equipped with threaded holes to mount the chassis mounting bush, two lifting eyes and a breather cartridge for the transfer box breather pipe. The breather pipe allows an equalization between atmospheric and internal transfer box pressure.

Rear Casing Assembly
The rear casing assembly provides the location for the rear output flange bearing, the transfer box motor and the oil fill and drain plug. Fins are cast into the rear casing assembly to improve the heat dissipation. The transfer box unit number is stamped into the rear housing.

OIL PUMP
An oil pump assembly is located in the front casing to provide lubrication for the bearings and rotary components through cross-drillings in the input shaft. A flat-sectioned coupling on the input shaft drives the rotor of the pump-, the stator is fixed to the front housing assembly. A tube is attached to the pump, which leads into a calm suction area at the bottom of the two casing assemblies. The collector magnet in the suction area of the pump collects any metallic debris.

CHAIN DRIVE
The chain-drive transfers drive from the center differential to the front output flange. A 3/8' pitch chain connects the sprocket on the transfer box input shaft with the sprocket on the front output flange. As both sprockets have the same number of teeth, the rotational speed of both sprockets is identical.

TRANSFER BOX MOTOR





The PWM controlled DC motor, located on the rear casing assembly, has an integrated worm gear reduction drive. The transfer box motor provides the necessary movement to perform the high/low range change and the multiplate clutch actuation.

An internal position sensor checks the rotational movement of the motor.

A temperature sensor is located within the motor housing.

Transfer Box Motor Solenoid





The solenoid switches the power flow on the actuation system between high/low range change mode and clutch control mode. When the solenoid is energized, the solenoid pin deploys and activates the clutch control mode. When the solenoid is de-energized, the internal spring rejects the solenoid pin and activates the high/low range change mode.

NOTE: In order to replace the solenoid in service, the solenoid must be energized using the diagnostic tool.

Motor Position for Clutch Control Mode





To actuate the multiplate clutch, the transfer box control module energizes the solenoid (3). The solenoid pin pivots the solenoid shift fork (2), which engages the shifting sleeve (5) into the dogteeth on the clutch control disc (4). The rotational movement of the motor shaft (1) is then linked to the clutch control disc via the shifting sleeve.

This is the normal operating mode of the transfer box. In this position, the range change function is disengaged and mechanically locked.

Motor Position for High/Low Range Mode





To actuate the high/low range change, the transfer box control module de-energizes the solenoid (3). A spring in the solenoid retracts the solenoid pin and rotates the solenoid shift fork (2). This engages the shifting sleeve (4) to the dogteeth on the high/low actuation cam (5). The rotational movement of the motor shaft (1) is then linked to the cam.

In this position, the multiplate clutch is open, the differential cannot be locked and torque cannot be biased. Once the range change is complete the system returns to clutch control mode. In the event of an electrical failure, the motor will default to this position.

CENTER DIFFERENTIAL ASSEMBLY





The center differential assembly is the primary feature of the transfer box. Torque is transmitted through the center differential carrier and distributed to the differential gears and the front and rear output flanges. The planetary gear set, for the high/low range change function, is also an integral part of the center differential assembly.

The assembly comprises 3 differential pinion gears (4) and shafts (5), which are equally spaced within the center differential carrier (3). The differential shafts have a rigid connection to the differential carrier. Located between the pinion gears are 3 planetary pinion gears (6) and shafts (7). The planetary sun gear (8) and two differential side gears (10) are located in the center line of the carrier.

The planetary ring gear (2) is supported in both directions by the differential casing and the differential cover (9). The planetary ring gear is connected to a shifting sleeve, which is engaged in either high or low range.





The multiplate clutch basket (11), which is welded to the differential casing, supports the friction plates, the dogteeth (12) for high range engagement and the synchronization cup and spring (1) for the 'shift-on-the-move' function.

When high range is engaged, the shifting sleeve (4) connects to the differential carrier via dogteeth (1). The planetary ring gear (3), via the shifting sleeve, and the planetary pinion gears (5), via the planetary shafts, are also attached to the differential carrier. The planetary gear set rotates as one unit and therefore turns the differential side gear with a 1: 1 ratio.

In low range the motor moves the shifting sleeve (4) in the direction of the low range dogteeth (5). The low range dogteeth, with the synchronization cup and spring, are fixed to the rear carrier assembly (6). When the shifting sleeve is engaged with the low range dogteeth, the planetary ring gear (3), via the shifting sleeve, is stationary and the planetary pinion gears (2), via the planetary bolts, turn the differential side gears with 2.93: 1 ratio.

High Range Actuation Sequence





The rotational movement of the motor shaft turns the shifting cam (3) to high range position. The shifting cam then moves the shifting sleeve (1), via the high/low shifting fork (2), into the high range position. After the synchronization sequence, the planetary ring gear is connected to the high range dogteeth, via the shifting sleeve, on the differential carrier. In this position, the input speed equals the output speed, which equates to a high range ratio of 1:1.

Low Range Actuation Sequence





The rotational movement of the motor shaft (4) turns the shifting cam (3) into low range position. The shifting cam then moves the shifting sleeve (1) of the center differential assembly via the high/low shifting fork (2) into low range position. After the synchronization sequence, the planetary ring gear is connected to the low range dogteeth, via the shifting sleeve, on the rear carrier assembly. The output speed is then reduced to a ratio of 2.93: 1.

MULTIPLATE CLUTCH ASSEMBLY





The multiplate clutch assembly for both center and rear differentials act in a similar way. The aim of the multiplate clutch assembly is to prevent excessive differential slip and therefore maximize the traction performance of the vehicle. This is fundamentally different from the 'braked' traction control, which can only counter act differential slip when it occurs.

A certain amount of differential slip is required to allow the vehicle to turn corners and to remain stable under control of the Anti-lock Braking System (ABS). The transfer box control module monitors the driver's demands through primary vehicle controls and automatically sets the slip torque at the differentials. The system is completely automatic and does not require any special driver input.

The multiplate clutch assembly actively controls the torque flow through the center differential and optimizes the torque distribution in the driveline. The clutch assembly biases the torque from the transmission to the axle and wheels with the higher grip and prevents the wheels with the lower grip from spinning.

The multiplate clutch assembly comprises the sprocket (7), which is connected to the front differential side gear, the motor levers (5) with the ball ramp mechanism (6), the clutch hub (1) as support for the clutch plates (3), the clutch piston (4) to generate friction between the clutch plates, and a pack of cup springs (2) to return the clutch piston into its original position.

One set of friction plates are connected to the clutch hub-, the other set of friction plates are connected to the multiplate clutch basket, which is welded to the center differential housing.

Multiplate Clutch Actuation





TRANSFER BOX MOTOR LEVERS IN INITIAL POSITION; MULTIPLATE CLUTCH IN OPEN CONDITION

TRANSFER BOX MOTOR IN END POSITION; MULTIPLATE CLUTCH IN CLOSED CONDITION





By turning the clutch control disc (3), via the motor shaft (2), the motor levers (4) are rotated relative to each other. This relative movement acts on 5 balls (5) in a ramp mechanism between the two levers and give a defined axial movement. The movement forces the clutch piston (1) to induce friction between the plates supported by the clutch hub and the plates supported by the clutch basket on the differential carrier. This frictional force inhibits the differential rotation-, the differential carrier and front differential side gear are locked together.

RANGE CHANGE SELECTION SWITCH





The range change selection switch is located behind the main transmission selection lever in the center console. The switch is a 3-position momentary action center-sprung device. The driver pushes the lever forward to select high range and back to select low range.

The switch housing provides the location for a sliding contact. When the switch is moved to the high or low position, it completes a momentary connection to 12V with one of two micro-switches located at each end of the switch. These micro-switches correspond to the high or low range positions.

An internal spring returns the selector lever to the center position when the switch is released.

HIGH/LOW POSITION SENSOR





The high/low position sensor converts the pivotal movement of the high/low fork into a PWM signal on the input. The PWM signal of the position sensor differs between high range and low range. The control module checks this signal and informs the driver, via the instrument cluster and the range change selection switch LEDs, if a range change is in progress or has been completed.

HIGH/LOW RANGE CHANGE LED





The 2 high/low range change LEDs adjacent to the range change lever are illuminated by the control module. The LEDs -one for each range - illuminate to indicate range change and status. The LED corresponding to the current selected range will be continuously illuminated. When a change of range is selected, the LED for the target range will flash when change commences, while the current range LED remains continuous. Once the target range has been achieved, the LED will be continuously illuminated-, the previous range LED will extinguish.

If both LEDs are flashing, a transfer box fault is present or the transfer box is in undefined range and may require calibration.

TRANSFER BOX CONTROL MODULE





The transfer box control module controls the high/low 'shift-on-the-move' actuation and the multiplate clutch actuation. The control module is located in the passenger side E-box, next to the Engine Control Module (ECM), behind the battery in the engine compartment.

The control module is connected to the Controller Area Network (CAN) bus and controls the transfer box operation using
CAN messages from other control modules on the network.

The control module memorizes the position of the transfer box motor when the ignition is switched off.

The transfer box control module uses the same actuator to control both range change function and application of center differential locking torque. The module uses position feedback from the actuator to provide smooth range changing capability and graduated application of locking torque appropriate for the current driving conditions. Range change can be carried out while moving providing the transmission is in neutral and the vehicle is below the speed necessary for the requested range change.

The control module uses a series of programmed shift maps to control the synchronization speed and ensure that a maximum shift time of approximately one second is achieved.

If the control module is replaced, a self-calibration routine must be performed using T4.This procedure must also be performed if the transfer box motor assembly is replaced.

Default/Limp-home Strategy





If a fault occurs with the transfer box, the transfer box control module or one of the required input signals, the control module records a fault code and will respond appropriately to provide the highest level of system capability under the specific fault conditions. The following fault states are possible:

If a driveline over-temperature condition has occurred, clutch control will be re-enabled and the warnings will disappear after the driveline has been allowed to cool. There is no need to seek service assistance following an over-temperature event.

If clutch control or Range change is not possible due to a permanent fault the driver must seek service assistance at the earliest opportunity.

If the system suffers a fault which causes the transfer box to fail in neutral, the control module is designed to continue attempting to engage the requested range or return to its original range for a fixed number of attempts. If this is not successful and the low range lamp is still flashing the driver should bring the vehicle to a halt and attempt the range change again while stationary. If this does not work after a number of attempts, key off for 30 seconds, restart engine and request range change again while stationary. The driver must seek service assistance at the earliest opportunity.

Transfer Box Control Module Inputs
Control module connector pin-out details can be found in the Workshop Manual - Description and Operation.

The transfer box control module receives the following inputs:
^ CAN bus messages
^ Range change selection switch
^ High/low position sensor
^ Transfer box actuator motor temperature sensor
^ Transfer box actuator motor position sensor

CAN Bus Messages
The transfer box control module is connected on the CAN bus and controls transfer box operation using CAN messages from other control units on the network. Wheel speed, vehicle acceleration, engine torque and speed, gear information from the automatic transmission, temperature information, car configuration, axle ratios and Terrain Response TM mode inputs, are some of the main signals received by the control module.

In the event of a CAN bus failure the following symptoms may be observed:
^ Shift from high to low or low to high inoperative
^ Instrument cluster low range warning lamp inoperative
^ Warning messages or lamps displayed in instrument cluster.

Range Change Selection Switch
The transfer box control module receives a momentary signal from the range change selection switch when a range change is selected. The module uses the signal for system control to achieve the requested range.

High/Low Position Sensor
The control module monitors the sensor signal and informs the driver, via the instrument cluster and the range change selection switch LEDs, if a range change is in progress or has been completed.

Transfer Box Control Module Outputs
The transfer box control module sends the following outputs:
^ CAN bus messages
^ Key interlock solenoid
^ High/low range change LED
^ Transfer box motor and solenoid.

CAN Bus Messages
The control module sends transfer box status messages via the CAN bus to other control modules on the network. High/low status, clutch torque and default mode status are some of the main signals sent.

Key Interlock Solenoid
The transfer box control module signals the key interlock solenoid to lock the key in the ignition barrel and prevent it from being removed when the transmission is not in the 'Park' position.

High/Low Range Change LED
The control module controls illumination of the High/Low Range Change LED based on signals from the High/Low position sensor.

Transfer Box Motor and Solenoid
The transfer box control module signals the transfer box motor and solenoid for switching between high/low range change mode and clutch control mode.

INSTRUMENT CLUSTER





The low range status indicator in the instrument cluster takes the form of a mountain symbol. The indicator has the following logic:
^ Lamp on: low range
^ Lamp off: high range
^ Lamp flashing: range change in progress/range undefined/range fault.
Transfer box messages are displayed in the message center, accompanied by chimes from the instrument cluster sounder.








The following table lists the message center transfer box messages and associated chimes:

DIAGNOSTICS
The transfer box control module stores faults as Diagnostic Trouble Codes (DTC's), which can be retrieved using T4.A complete list of DTC's is available in the Workshop Manual.

Clutch and Range Change Mechanism Calibration
In order for the range change mechanism to function correctly, the transfer box control module must be calibrated to the mechanical dimensions of the transfer box that it is connected to.

The calibration routine must be performed if one of the following occurs:
^ The switch is changed
^ The transfer box control module is changed
^ The transfer box or range position sensor is changed
^ Vehicle or transfer box control module fault has caused the transfer box to revert to an undefined range.

SERVICE
BASIC DIMENSIONS (MILLIMETERS)





The transfer box weighs 41.55 kg (91.61 lbs.) when filled with oil. The unit requires 1500 ml (1.6 qt.) � 2% of oil from empty.

The oil used in the transfer box is Shell TF 0753, which has been specially developed by Magna Steyr and Shell. The oil contains unique additives which enhance the transfer box operation. No other oil should be used in the transfer box.





A unique grease - Weicon anti-seize montagepaste grau TL 7391 - needs to be applied to the input shaft spline when installing or reinstalling the transfer box.








TRANSFER BOX CONTROL DIAGRAM

Four-Wheel Drive (4WD) Control Module
Removal
1. Disconnect the battery ground cable.
2. Remove the battery.





3. Remove the four wheel drive control module cover.
^ Depress the 2 clips.
^ Release the cover.





4. Release and remove the four wheel drive control module.
^ Depress the 2 clips.
^ Disconnect the 3 electrical connectors.

Installation
1. To install, reverse the removal procedure.
2. Program a new control module using T4.