power to the wheel with the most traction. Figure 16-21 is
an exploded view of the cone differential.
Note that both clutch-plate and cone differentials
require special limited-slip gear oil. Using ordinary gear oil
in limited-slip differentials will cause the discs and plates
or cones to slip and vibrate during turns.
The ratchet differential, nicknamed a Detroit locker,
uses a series of cams and ramps to direct power to the
wheel with the most traction. Its operation depends on rel-
ative wheel speed, rather than on wheel traction. The
ratchet differential transfers power through a set of teeth
that can be engaged and disengaged. This kind of engag-
ing teeth system is sometimes called a dog clutch. The
series of cams and ramps disengage the teeth of the dog
clutch on the side of the wheel with the least traction. An
example of the ratchet differential is shown in Figure 16-22.
For straight-ahead driving, both sets of teeth are
engaged, and the differential case and wheels turn at the
same speed, Figure 16-22A. During turns or when one
wheel loses traction, the speed difference between the
wheels causes the internal cam and ramp to disengage the
teeth on the side of the faster moving wheel, Figures 16-22B
and 16-22C. All power is then sent through the other wheel.
Since the faster moving wheel is always the one that
is slipping, power always goes to the wheel with traction.
On turns, the loss of power to the outer wheel is not
noticeable. This design is durable and does not require
special gear oil, but it is often rough and noisy in opera-
tion. It is usually used in off-road and racing vehicles.
The Torsen differential is a locking differential using
complex worm gearsets. The gearsets include worms (drive
gears) and worm wheels (driven gears). The Torsen differ-
ential has been available since the 1960s as a high-
performance replacement unit for standard differentials. It
is now being offered as original equipment on some
European cars. The basic mechanical principle of this
differential is that while the worm can drive the worm
wheel, the worm wheel cannot drive the worm.
As shown in Figure 16-23, the Torsen differential has
two central worms. For purposes of clarity, these will be
referred to as axle gears. One axle gear is attached to each
axle shaft. Worm wheels ride on and are driven by the axle
gears. The worm wheels are held in place by the differen-
tial case. Spur gears machined on the ends of the worm
wheels mesh and form the only connection between the
two axle shafts. Engine power drives the differential case,
and the worm wheels, held by the case, turn with it. The
worm wheels cannot turn the axle gears, so they lock
themselves to the gears. In this way, power is transmitted;
the axle gears and axles are locked to the case, and they
rotate with it.
320 Manual Drive Trains and Axles
Differential case
Side gears
Cone clutch
Lubrication
grooves
Lubrication
Coil
spring
Pinions
Figure 16-20. Study the construction of the cone differential.
The operation of this limited-slip differential is similar to that of
the clutch-plate differential. Pressure on the side gear of the
wheel with traction causes the cone to be pressed into the
dished area of the differential case, locking the case to the drive
axle on that side. (DaimlerChrysler)
Case
Clutch cone/
side gear
Spring
Spider gear
Pinion thrust washer
Spring block
Clutch cone/
side gear Case
Pinion
shaft
Spring
block
Figure 16-21. Exploded view of the cone differential shows the relationship of parts. Grooves in the cones help to solidly engage
the case. (DaimlerChrysler)