Differential Assembly: Description and Operation

FINAL DRIVE UNIT

Fig.1:

The transmission unit is a 'Powr-Lok' limited slip final drive (Fig.1). The unit can be identified by a tab bearing the letters 'PL' situated under one of the bolts securing the rear cover.

A 'Powr-Lok' differential differs from a conventional bevel gear unit by the addition of clutch plates, which are loaded by input torque to oppose rotations of the output shafts relative to the differential cage. Clutch plates are splined to the cage, and their mating discs to the outside bevels. The loading between plates and disc increases with input torque, due partly to the separating forces of bevels, and also to the bevel pinion cross-shafts being carried on ramps instead of being positively located in the cage.

Increase in input torque causes the cross-hafts to move 'up' the ramps and, by pressing plates and discs together, to 'lock' the differential, this gives the effect of a differential-less axle at maximum torque without increasing the disadvantages of this type of axle in low-torque conditions.

Some low-torque stiffness, to reduce on-wheel spin on ice, is provided by forming the outer plates as Belleville washers to produce compression between the plates and discs. If one wheel is held and the propeller shaft is disconnected, a torque is required to turn the other wheel.