Front Axle Description and Operation
The front axle consists of the following components:
• | Differential Axle Housing |
• | Right and Left Axle Shafts |
The Dana 70 monobeam front axle has an open knuckle design. Other than
the unique parts for front-wheel drive these axles are mechanically identical
to Model 70 rear axle assemblies. It is a full floating axle design. The axle
shafts are retained by the front wheel spindles. It is equipped with an open differential
which has a set of four gears. Two are side gears and two are pinion gears. Each side
gear is splined to an axle shaft so each axle shaft turns when the side gear rotates.
The pinion gears are mounted on a differential pinion shaft, and the gears are free
to rotate on this shaft. The pinion shaft is fitted into a bore in the differential
case and is at right angles to the axle shafts. Power is transmitted through the differential
as follows: the drive pinion rotates the ring gear. The ring gear being bolted to
the differential case, rotates the case, the differential pinion, and
as it rotates the case, forces the pinion gears against the side gears. When both
wheels have equal traction, the pinion gears do not rotate on the pinion shaft because
the input force on the pinion gear is equally divided between the two side gears.
Therefore, the pinion gears revolve with the pinion shaft, but do not rotate around
the shaft itself. The side gears, being splined to the axle shafts and in mesh with
the pinion gears rotate the axle shafts. If a vehicle were always driven in a straight
line, the ring and pinion gears would be sufficient. The axle shaft could be solidly
attached to the ring gear and both driving wheels would turn at equal speed. However,
if it became necessary to turn a corner, tires would scuff and slide because the differential
allows the axle shafts to rotate at different speeds. When the vehicle turns a corner,
the inner wheel turns slower than the out wheel and slows the front axle side gear
(as the shaft is splined to the side gear). The front axle pinion gears will roll
around the slowed front axle side gear, driving the front axle side gear wheel faster.
If the front axle were to be equipped with a limited slip or locking differential
this would create a torque steer situation due to the offset of the differential housing
and having the left axle shaft longer than the right axle shaft.
Manual Locking Hubs
The front axle is equipped with manual locking hubs. When actuated the locking
hub locks the hub and wheel and tire assembly to the halfshaft. When released, the
axle shaft is disengaged from the front disc brake hub and rotor and the wheel rotates
freely on the front wheel spindle. The manual locking hubs must be engaged and disengaged
by hand. To engage the hubs for 4-wheel drive, grasp the locking bar in the
center of the hub and rotate it clockwise to the LOCK position. The arrow on the locking
bar must line up with the marker on the hub at the LOCK position. To disengage the
hubs for the 2-wheel drive, grasp the locking bar and rotate it counterclockwise
toward the FREE position until the arrow on the locking bar is lined up with the marker
on the hub at the FREE position.