Lesson 2/Learning Event 2
Also, the axle is constructed so that the power flow can turn 90 in each direction (from
the propeller shaft to the right and left wheels). This is needed to direct the power flow to
the drive wheels on each side of the vehicle. This change of direction is done by the use
of worm gears or bevel drive gears. Notice that the pinion gear is the smallest and the
ring gear is the largest. These two gears provide a reduction in speed and change the
direction of the power flow.
As the vehicle moves around a turn, the wheels on opposite ends of the axle must turn at
different speeds. The wheel on the outside of the turn travels a larger circle or path than
the wheel on the inside of the turn. If both wheels were rigidly mounted to a solid shaft,
the tires would slide on the road surface when the vehicle turned a corner. The live axle
must, therefore, include some type of mechanism to prevent the wheels from sliding.
This mechanism is called the differential. It permits one wheel to turn faster than the
other one, while still driving both wheels. The output of the differential is transferred to
the wheels by axle shafts.
Types of Live Axles
Live axles are grouped into four general types, based upon the way that the load is
supported. An easy way to identify these axles is the manner in which the axle shafts are
mounted. The four types are the plain, semifloating, three-quarter floating, and full-
floating axles. Each rear live axle assembly consists of a gearbox or final drive in the
center and axle shafts extending to the wheels on either side.