Construction
Construction
The transfer box comprises three main assemblies; the main casing, the front output housing and the rear output housing.Both output housings and all cover plates are sealed to the main casing by sealant; mud and water ingress being prevented by mud shields located on the output flanges.
Main Casing
The main casing carries the mainshaft input gear, the intermediate gears and the differential, together with the high/low range gears, selector shaft and fork. The front and rear output housings are bolted to either side of the main casing.
Mainshaft input gear
The gearbox output shaft is splined into the mainshaft input gear which is supported by taper roller bearings. Input gear bearing pre-load is achieved by the use of a selective shim located in the bearing housing.
Front output housing
The front output housing carries the front output shaft and flange, high/low cross shaft, housing and selector and the differential lock selector shaft and fork.
The front output shaft is supported in the housing by a single bearing and is splined into the differential front sun gear.
Intermediate gears
The intermediate gear cluster is supported by the taper roller bearings located at each end of the cluster and runs on the intermediate shaft which, in turn, is supported at the front and rear by the main casing.
A selective spacer, positioned between the gears, pre-loads the intermediate gear bearings when the intermediate shaft nut is tightened sufficiently to achieve the correct 'torque to turn' of the intermediate gears.
Rear output housing
The rear output housing carries the output shaft and flange. A cable operated transmission brake is attached to the housing, the brake drum being attached to the output flange.
The rear output shaft is supported in the housing by a single bearing and is splined into the differential rear sun gear.
High/low selector
The high/low cross shaft is located in a housing bolted to the top of the output housing and is connected to the high/low selector finger which locates in a slot in the selector shaft.
Differential Assembly
The differential assembly is supported at the front and rear by taper roller bearings (11,12 & 21,22), the front bearing outer track is located in the front output housing and the rear bearing outer track is located in the main casing by the rear output housing. Bearing pre-load is achieved by means of a selective shim (13) located in the front output housing.
The differential rear shaft carries the low range gear (9), high/low selector sleeve and hub (4,5), high range gear (3) and bush and the differential rear bearing; these components being secured to the shaft by a special staked nut.
The differential assembly comprises front (19) and rear (2) half carriers with integral shafts and with sun (17) and planet (15) gears mounted on cross shafts (16) within the half carriers. Dished, non-selective thrust washers (14) control the engagement of the planet gears with the sun gears, while selective thrust washers (18) are used to control engagement of the sun gears and 'torque to turn' of the differential. The differential carrier halves are bolted together, a retaining ring providing positive location of the cross shafts.
NOTE: Excessive operation of the sun and planet gears, such as that which occurs during driving under slippery conditions without differential lock engagement, will result in premature wear of the thrust washers (14,18). This thrust washer wear can contribute to a complaint of 'clunk' on acceleration/deceleration.
The high/low selector shaft and fork (6,7) are located at the side of the differential, movement of the shaft, fork and selector sleeve being controlled by the high/low selector finger. A spring loaded detent ball fitted in the main casing, locates in grooves in the shaft..
Differential lock
The differential lock selector housing is bolted to the top of the output housing, the selector finger passes through the housing, locating in a slot in the differential lock selector shaft. The differential lock selector shaft passes through the selector fork which is located beneath a plate bolted to the side of the output housing. The selector fork engages the dog clutch sleeve with the differential rear shaft when the splines of the sleeve and differential rear shaft are aligned. A spring loaded detent ball fitted in the output housing locates in grooves in the shaft.
1999 - 2003 Model Year
The function of the differential lock on these vehicles is performed by the Electronic Traction Control System. However, for the purposes of 2 wheel rolling road testing, the differential lock components are retained. For all driving conditions however, the differential lock must be set in the unlocked position. Engagement of the lock disables the traction control feature and inhibits correct operation of the electronic brake distribution and hill descent features.
It will also be necessary to disconnect the propeller shaft from the transfer box output shaft driving the axle whose wheels are NOT on the rolling road. The lock may be engaged/ disengaged by using a 10 mm open ended spanner on the flats machined on the differential lock selector shaft.
2004 Model Year Onward
The differential lock must be engaged for 2 wheel rolling road testing. It will also be necessary to disconnect the propeller shaft from the transfer box output shaft driving the axle whose wheels are NOT on the rolling road. In addition, the ETC system must be deactivated by either, removing a fuse (10A fuse 28 in the passenger compartment fusebox, labelled ABS) or disconnecting the ABS modulator pump. This must be done with the ignition switched off.
Note that the SLABS ECU may record a system fault. The lock can be engaged or disengaged using the selector lever.
