Rear Drive Unit (RDU) Sectional View
| ITEM | DESCRIPTION |
|---|---|
| 1 | AWD valve block |
| 2 | RDU pump |
| 3 | Pre-load nut |
| 4 | Drive flange |
| 5 | Oil seal |
| 6 | Mounting bracket |
| 7 | AWD Control Module (AWDCM) |
| 8 | Taper roller bearing |
| 9 | Pinion shaft and drive gear |
| 10 | Collapsible spacer |
| 11 | Right clutch pressure connection P1 |
| 12 | Ball bearing |
| 13 | Right inner disc carrier |
| 14 | Oil seal |
| 15 | Right cover |
| 16 | Clutch pack |
| 17 | Outer disc carrier |
| 18 | Casing |
| 19 | Crown wheel shaft and drive gear |
| 20 | Intermediate housing |
| 21 | Left outer disc carrier |
| 22 | Left cover |
| 23 | Left inner disc carrier |
| 24 | Left clutch pressure connection P2 |
| 25 | Hydraulic fluid reservoir |
The RDU comprises a main casing, an intermediate casing and left and right covers. Within the casing is a crown wheel drive gear and shaft, a pinion drive gear and shaft, two wet, multiplate clutch packs and two hydraulically actuated pistons.
Externally mounted on the casing is an AWD valve block which contains four solenoid operated pressure control valves and an electrically operated hydraulic pump. The All Wheel Drive Control Module (AWDCM) is located externally on the casing.
The casing is filled with oil for lubrication of the pinion and crown wheel drive gears and bearing and also lubrication and cooling for the multiplate clutch packs. A fill/level plug is located on the left cover and a drain plug is fitted to the underside of the casing.
The intermediate casing allows for the internal components to be assembled within the main casing and also houses the left multiplate clutch pack assembly.
The crown wheel drive gear is mounted longitudinally across the RDU on a crown wheel shaft. The drive gear is a low-offset hypoid bevel gear configured for minimal power loss across the speed range. Both ends of the crown wheel shaft have splines which mate with corresponding splines in the outer disc carrier of the multiplate clutch pack.
The crown wheel shaft is supported on opposing taper roller bearings which are pressed into the casing and the intermediate casing.
The pinion drive gear and shaft is locked in the casing at 90 degrees to the crown wheel drive gear. The pinion drive gear shaft is supported in the housing on opposing taper roller bearings. The pinion drive gear shaft is retained in the casing with a pre-load nut. The outer end of the pinion gear is splined and mates with the drive flange. The drive flange is secured on the pinion gear by the pre-load nut.
A collapsible spacer is located between the taper roller bearings. The collapsible spacer holds the taper roller bearings in alignment and also collapses under pressure applied by the pre-load nut. This allows the pre-load nut to be tightened to a predetermined torque, which collapses the spacer, setting the correct taper roller bearing pre-load and therefore the correct meshing of the teeth of the pinion drive gear and the crown wheel drive gear.