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TM 9-8000
Figure 29-2. Conventional Driveshaft.
lock all the parts, making them rotate as a unit when the
axle shaft fast to the differential case and differential
drive differential ring gear is turned by the differential
drive ring gear. This forms a rigid connection between
drive pinion.
the two axle shafts and makes both wheels rotate at the
same speed as the differential drive ring gear while the
b. Turns.  When the wheels rotate at different
differential lock is engaged. This device is used very
seldom, probably because a driver often forgets to
speeds, as' they do when making a turn, the slowing
disengage the differential lock before the differential
down of the inner wheel decreases the rotation of its axle
action is required again. Automatic devices for doing
shaft and differential side gear with respect to the
almost the same thing have been designed.  One of
differential drive ring gear and the differential case. The
these, which is used rather extensively today, is the high-
case forces the differential pinions to rotate along the
traction differential.  It consists of a set of differential
inner differential side gear, advancing the opposite side
pinions and side gears, which have fewer teeth, and a
gear an equivalent amount with respect to the differential
different tooth form from the conventional gears. Figure
case. The outer wheel thus turns at a higher speed than
29-3 shows a comparison between these and standard
the inner wheel. If the differential drive ring gear makes
gears. These differential pinions and side gears depend
four revolutions while the inner wheel is making one, the
on a variable radius from the center of the differential
outer wheel will rotate seven times.
pinion to the point where it comes in contact with the side
gear teeth, which is, in effect, a variable lever arm. As
29-3.  High-Traction Differential Gears (Fig. 29-3).
long as there is relative motion between the pinions and
A fault in the conventional differential is that if one
side gears, the torque is divided unevenly between the
driving wheel loses traction and spins, the other wheel,
two driving shafts and wheels; whereas, with the usual
which has more traction, remains stationary and does
differential, the torque is divided evenly at all times. With
not drive the vehicle. In order to overcome this, several
the high traction differential, the torque becomes greater
devices have been employed from time to time. One
device is the hand-controlled differential lock. This is a
dog clutch, controlled by a hand lever, that clutches one


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