L322 Range Rover System Description and Operation
TRANSFER BOX
41-22
DESCRIPTION AND OPERATION
Torsen® Differential Operation
The input torque from the transmission is passed via the synchroniser sleeve to the differential housing. The torque
is then transmitted from the housing, through the three pairs of pinion gears and into the differential side gears.
The side gears have opposite handed helical gear forms and intermesh with only one of the pinion gears in each pair.
The pinion gears intermesh with each other as well as individually meshing with only one of the side gears. Between
each pinion gear and the differential housing and on either side of each side gear are friction surfaces or pairs of thrust
washers and friction thrust washers. The pairs of thrust washers control the torque biasing function of the differential.
During normal driving, the differential housing rotates at the same speed as that of the input shaft in high range or the
planetary carrier in low range. If there is no differential motion between the front and rear propeller shafts, then the
differential gear and therefore the side gears will have no relative motion and the whole unit functions as a normal
differential.
If the front or rear wheels suddenly loose traction, a large differential motion between the front and rear propeller
shafts occurs as the slipping wheels begin to accelerate or spin. In this case with a normal differential, the torque
applied to the non-slipping wheels is lost through the differential. With the Torsen® differential, as soon as one wheel
begins to slip, the front and rear output side gears are encouraged to rotate at different speeds. With the side gears
in constant mesh with their relative pinion gears, and the pinion gears meshing with each other, the differential begins
to generate axial and radial thrust loads.
The thrust loads are generated as a result of the helical gear form of the pinion and side gears and they are exerted
onto the thrust washers and friction thrust washers within the differential housing. The friction thrust washers generate
a resistance to the relative motion and produce a locking effect within the differential. This ensures that the torque is
always directed, or biased, towards the propeller shaft with the highest traction and ensures that the vehicle maintains
continuous motion on slippery or uneven surfaces. This action takes place progressively and the driver will be
unaware of its operation.
