In part-time four wheel drive vehicles, drive is transmitted through the rear final drive, in all drive ranges. Drive is only transmitted through the front axle final drive, when a four wheel drive range is selected.
The final drive gears are normally a hypoid bevel crown wheel and pinion.
The final gear ratio reduction must be the same in both front and rear axles, so that when four wheel drive is engaged, the driving wheels rotate at the same speed.
The crown wheel is bolted to a differential case, and drive is transmitted through the case and differential gears and axle shafts to the road wheels.
Taper roller bearings support the differential case and the pinion in the carrier. Provision is made for pre-load and backlash adjustment, and for positioning the pinion in relation to the crown wheel.
