Transfer Box - Operation
OperationGeneral
The selection of high/low range is selected by the driver using a switch adjacent to the transmission selector lever. A range change can only be performed when the transmission selector lever is in neutral, position "N". The accelerator pedal must not be depressed when a range change is in progress.
If high or low range is requested and the transmission selector lever is a position other than "N" or "P", the instrument pack message center will display "SELECT NEUTRAL".
NOTE: With the transmission selector lever in "P" the range change will not take place and the "SELECT NEUTRAL" message will not be displayed.
When low range is selected, the low range "mountain" symbol will flash when the range change is taking place and then remain illuminated when the range change is complete. The instrument pack message center will display "LOW RANGE" for approximately 3 seconds followed by a chime from the instrument pack to confirm that the range change has been completed. Only "D" and "Manual mode" are available on the transmission, the "Sport mode" selection is not available.
When high range is selected, the low range "mountain" symbol will flash when the range change is taking place and then extinguish when the range change is complete. The instrument pack message center will display "HIGH RANGE" for approximately 3 seconds followed by a chime from the instrument pack to confirm that the range change has been completed.
The design of the transfer box allows range changes when the vehicle is moving, within set limitations as follows:
^ High to Low - at speeds not exceeding 10 mph (16 km/h)
^ Low to High - at speeds not exceeding 30 mph (48 km/h).
If the vehicle speed is higher than the parameters given above, the instrument pack message center will display "SLOW DOWN". When the correct speed range is reached, the message will be deleted and the range change will commence.
A road speed of less than 2 mph (3 km/h) is interpreted by the transfer box ECU as a static shift (vehicle not moving). In this instance the driver must use the shift lock procedure of operating the brake pedal to allow the selector lever to be moved from "N" to "D" after the range change has been performed.
High range should lee used for all normal road driving and also for off-road driving across dry, level terrain. Low range should only be required where low speed maneuvering is necessary, such as reversing a trailer, negotiating steep slippery surfaces or boulder strewn terrain. 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.
Neutral Selection
The transfer box can be moved into a neutral position for towing the vehicle. The vehicle must not be towed with the transfer box in high or low range. The transmission must also be in the neutral position. If neutral cannot be selected on the transmission, the vehicle must not be towed.
To engage the transfer box in neutral, switch the ignition to position 11 and select neutral "N" on the transmission selector lever. Insert a spare 5 Ampere fuse or greater into the empty fuse position 37 in the passenger compartment fuse box, which is located at the back of the glovebox. Fuse position 37 can be identified using the legend on the fusebox cover.
Once the fuse is installed, the actuator will engage the transfer box in the neutral position.
Once in neutral, the low range "mountain" symbol in the instrument pack flashes permanently and "TRANSFER BOX NEUTRAL" is displayed in the instrument pack message center.
Cold Climate Operation
In low ambient temperatures, there may be an increased time delay for the transmission to select neutral. To prevent the transfer box changing range before the transmission has selected neutral, the transfer box ECU contains software to delay the range change.
The transfer box ECU receives a transmission fluid temperature message on the CAN. If this temperature is 5°C (41°F) or below, the transfer box ECU initiates a nominal delay in the range change to allow the transmission to engage neutral. The delay period is dependent on transmission fluid temperature.
High Range Operation
In high range, the torque input from the transmission is passed to the transfer box input shaft. The position of the synchronizer sleeve couples the shaft directly to the differential housing. The differential splits the torque between the two side gears. One side gear is connected lay splines and passes the torque to the rear output flange. The second side gear is connected to the chain drive sprocket and passes the torque, via the chain, to the front output flange.
Low Range Operation
In low range, the torque input from the transmission is passed to the transfer box input shaft. The synchronizer sleeve is moved and connects the planetary carrier to the differential housing. The torque from the transmission is now directed through the sun gear of the epicyclic gearset and, via the pinion gears and pinion gear shafts, into the planetary carrier. The annulus gear of the epicyclic gearset is secured inside the casing and generates the low range ratio of 2.69:1. The torque is then passed, via the synchronizer sleeve, to the differential housing where it is split between the two side gears. One side gear is connected lay splines and passes the torque to the rear output flange. The second side gear is connected to the chain drive sprocket and passes the torque, via the chain, to the front output flange.
Torsion (R) Differential Operation
The input torque from the transmission is passed via the synchronizer sleeve to the differential housing. The torque is then transmitted from the housing, through the three pairs of pinion gears and into the differential side gears.
The side gears have opposite handed helical gear forms and intermesh with only one of the pinion gears in each pair. The pinion gears intermesh with each other as well as individually meshing with only one of the side gears. Between each pinion year end the differential housing and on either side of each side gear are friction surfaces or pairs of thrust washers and friction thrust washers. The pairs of thrust washers control the torque biasing function of the differential.
During normal driving, the differential housing rotates at the same speed as that of the input shaft in high range or the planetary carrier in low range. If there is no differential motion between the front and rear propeller shafts, then the differential gear and therefore the side gears will have no relative motion and the whole unit functions as a normal differential.
If the front or rear wheels suddenly loose traction, a large differential motion between the front and rear propeller shafts occurs as the slipping wheels begin to accelerate or spin. In this case with a normal differential, the torque applied to the non-slipping wheels is lost through the differential. With the Torsion (R) differential, as soon as one wheel begins to slip, the front and rear output side gears are encouraged to rotate at different speeds. With the side gears in constant mesh with their relative pinion gears, and the pinion gears meshing with each other, the differential begins to generate axial and radial thrust loads.
The thrust loads are generated as a result of the helical gear form of the pinion and side gears and they are exerted onto the thrust washers and friction thrust washers within the differential housing. The friction thrust washers generate a resistance to the relative motion and produce a locking effect within the differential. This ensures that the torque is always directed, or biased, towards the propeller shaft with the highest traction and ensures that the vehicle maintains continuous motion on slippery or uneven surfaces. This action takes place progressively and the driver will be unaware of its operation.