Differential Assembly: Description and Operation

DESCRIPTION

Fig.1:

The transmission unit is available in either 'Powr-Lok' or non 'Powr-Lok' form. When a 'Powr-Lok' is specified it is 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 loaded by input torque to oppose rotation of the output shafts relative to the differential cage. Clutch plates are splined to the cage, and their mating discs to the output bevels. The loading between plates and discs increases with input torque due partly to the separating forces of the 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 shafts 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 one-wheel-spin on ice, is provided by forming the outer plates as Belleville washers to produce compression between plates and discs. If one wheel is prevented from turning and the propeller shaft is disconnected, a torque is required to turn the other wheel.