Power Transfer Unit Internal Components
| ITEM | DESCRIPTION |
|---|---|
| 1 | Vee seal |
| 2 | Oil seal |
| 3 | Ball bearing |
| 4 | Input shaft engagement ring |
| 5 | Synchronizer sleeve |
| 6 | Crown wheel drive gear |
| 7 | Pinion shaft drive gear |
| 8 | Pinion shaft |
| 9 | O ring seal |
| 10 | Piston |
| 11 | Circlip |
| 12 | Detent |
| 13 | Synchronizer selector fork |
| 14 | Input shaft |
The crown wheel drive gear is mounted longitudinally across the unit. The gear is a low-offset hypoid bevel gear configured for minimal power loss across the speed range. The left end of the crown wheel shaft has splines which mate with corresponding splines in the synchronizer sleeve. The crown wheel shaft is hollow which allows for the fitment of the right halfshaft. The halfshaft is located through the crown wheel shaft and the input shaft and mates with splines in the transmission differential. The halfshaft is driven by the transmission differential and receives no drive from the PTU.
The crown wheel shaft is supported in the casing on opposing taper roller bearings which are pressed into the casing and sealed with an O ring seal. The casing is fitted with a triple edge oil seal on the outer end of the right casing which directs dirt and moisture away from the area of the drive gear. Another seal is fitted which prevents the ingress of dirt and moisture between the drive gear and right halfshaft.
The pinion drive gear is locked in the casing at 90 degrees to the crown wheel drive gear. The pinion drive gear is supported in the casing on opposing taper roller bearings. The pinion gear 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.
The pinion drive gear is locked in the casing at 90 degrees to the crown wheel drive gear. The pinion drive gear is supported in the casing on opposing taper roller bearings. The pinion gear 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 outer taper roller bearing and a shoulder on the pinion shaft. The collapsible spacer holds the taper roller bearing 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.