Limited slip differentials allow differential action under normal driving conditions.
However, when road conditions are not normal a limited slip differential reduces or prevents differential action, so that a wheel cannot spin, and drive is maintained to both wheels.
This limited slip differential uses a multi-plate clutch pack between each side gear and the differential case.
Each clutch pack has two different types of flat steel plates, placed alternately in the pack.
One type has internal splines which mate with splines on the side gear pressure ring. The other has driving lugs which locate in slots in the case.
One plate on the outside is dished, or cup shaped, to provide initial tension on the clutch pack when the two halves of the case are assembled. Four differential pinions are mounted on two driving pins, at right angles to each other, so that they mesh with the side gears.
The pinion shafts are relieved, so as not to make contact at their intersection. The ends of the shafts have 2 flat surfaces forming wedge shapes, which fit into similar wedges in the case.
In straight-ahead driving, the driving force through the crown wheel to the differential case, causes the pinion shafts to rotate end over end. This transfers the drive through the pinion gears and the side gears to the axles.
There is no relative motion between the gears.
However, the resistance at the road wheels forces the pinion shafts up the incline formed by the wedges in the case. This forces the shafts apart so that the pinion gears exert a greater force on the side gears, and on the clutch packs.
This locks the side gears to the case, preventing any sudden spinning of either wheel.
It also assists in maintaining the straight line stability of the vehicle in cross winds, because the locked clutches reduce yawing of the driving axles.
Under normal operating conditions, the driving torque is transmitted equally to each axle shaft and wheel. However, when patches of loose gravel or mud are encountered, the ratio of torque delivered depends on the traction available at each wheel.
The greatest amount of torque will be transmitted through to the wheel with the most traction.
When turning a corner, the limited slip differential gives normal differential action and permits the outer wheel to turn faster than the inner wheel.
At the same time, the differential applies the major driving force to the inner wheel, improving stability and cornering.
