Australian 4WD Action – July 2019

HOW DOES A

DIFFERENTIAL WORK?

Your diffs have a very important job. They transfer power from
the prop shaft through 90° to the axles, which in turn drives
the wheels. They also enable the two wheels on that axle to
rotate at differing speeds (hence the name) while you travel
around a corner.
As your tailshaft spins, it rotates the pinion shaft and pinion
gear, which turns the crown wheel. Attached to the crown
wheel is a housing called the hemisphere. Inside this are the
gears that transmit the power to the axles. Inside the
hemisphere of a typical open diff, you’ll find a smaller pair of
axle gears (which are splined to suit the axles), and a smaller
pair of spider gears (which enable the difference in axle speed
as you round a corner) 90° to the axle gears.
As your vehicle moves forward, the crown wheel turns the
hemisphere, which in turn drives the axle gears, and thus the
wheels. When you are travelling straight ahead with both tyres
on a solid surface, the axle gears are moving at the same
speed, so the spider gears remain stationary, simply following
the hemisphere as it rotates.
When you start to turn a corner, the planetary gears start to
rotate around the axle gears within the hemisphere, allowing
both wheels to turn at different speeds.
Lockers and LSDs essentially replace this hemisphere with
a different set of inner workings again. LSDs use clutch packs
to enable some slip while limiting how much, and lockers
essentially lock the axles together allowing no slip, when they
are engaged.

The^ meshing^ paint^ is^ placed^ on^ the^

crownwheel^ to^ see^ where^ the^ pinion^

contacts^ to^ ensure^ correct^ setup

The solid spacer on the left is a

much stronger design than the

collapsible spacer on the right

You can see by the wear on the teeth

that the pinion gear was contacting

on a weaker part of the crownwheel

which caused premature failure

This is what can happen

to your crownwheel

from poor setup

W

W

W

. 4
W
D
A
C
TI
O
N
.C
O
M
.A
U

(^07)
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