Lesson 2/Learning Event 2
Also, the teeth have the normal spur gear tooth shape so that, as one tooth comes out of
mesh on one side of the gear, the tooth on the opposite side does the same thing. Now,
look at the shape of the teeth on the high-traction gears. If the ring gear was forcing the
unit to rotate so the spider pinion was moving down, two teeth would be forcing the side
gears, axle shafts, and wheels to rotate, also. However, look at the difference in the
points of contact for the two teeth. The leverage from the center of the spider to the point
of contact for one tooth is much longer than that for the other tooth. If you recall the
principles of gears, you see that this arrangement will apply a greater force on the second
tooth.
High-traction type gearing works very well when only a small amount of wheel slippage
is involved. However, if one wheel is on a large piece of ice and the other wheel has
good traction, it will not provide enough change in torque to keep the one wheel from
spinning.
REAR AXLES
Axle shafts must be strong enough to deliver the twisting force necessary to move the
vehicle under all conditions.
The full-floating axle shaft is splined on one end to fit the splines of the differential side
gear. The other end contains a flange that can be bolted to the wheel hub, or it may be
splined and require a splined flange that slides onto the shaft first and is then bolted to the
hub.
Semifloating axles are mounted a little differently. Remember, they support some of the
weight of the vehicle, so the wheel end is tapered and the wheel hub is keyed to it and
held in place with an axle nut.
The axle housing is usually a steel casting that varies in size according to the vehicle
design and size. The housing mounts the wheels, axle shafts, final drive, and differential
assembly. Seats or flat surfaces are provided either on the top or bottom of the housing
for springs. On vehicles with more than one rear axle, torque rods are connected to arms
located on the top and bottom of the housing. Like the tandem trailer axles, the torque
rods and leaf springs keep the axles in position.
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