DIFFERENTIAL AND BEVEL GEAR
1. Pinion shaft. 2. Pinions (tour). 3. Bevel gear. 4.
Spider. 5. Side gears (two).
The gear on the transmission output shaft is
engaged with the transfer output shaft gear which sends
power through universal joints to the drive shafts. The
drive shafts are connected with splines to the pinion
shaft (1). The pinion shaft turns the bevel gear (3)
which is fastened to the differential case. The
differential case contains four pinions (2), installed on a
spider (4), and two side gears (5). The four pinions are
engaged at right angles with the two side gears. The
side gears are connected with splines to the inner ends
of the drive axles.
The differential makes the torque equal that goes
to both drive wheels. When one wheel is turning slower
than the other, as in a turn, the differential permits the
inside wheel to stop or slow in relation to the outside
When the machine is moving straight ahead with
equal traction under each drive wheel, equal torque on
each axle stops the pinions (2) so they will not turn on
the spider (4). This gives the same action as if both
drive wheels were locked on the same driving axle.
When loads that are not equal are put on the drive
wheels, as in a turn, forces that are not equal are put on
opposite sides of the differential causing the pinions (2)
to turn. When the pinions are turning, the inside wheel
slows or stops and increases the turning of the outside
wheel. This action causes the machine to be driven with
full power in a turn.
The hubs of the differential cases are installed on
the differential carrier with tapered roller bearings. The
pinions (2) turn on hardened steel bearings. Both the
pinions (2) and side gears (5) turn against thrust
washers which take the end thrust against the
The differential gets lubrication from oil thrown
about by the moving parts. Flat surfaces on the spider
permit passage of oil for lubrication to the pinion
bearings and the thrust washers.