PAWL
PAWL BLOCK
LUG
RETAINING PLATE
RATCHET RING
Fig. 118. Allen Gearless Differential
[Fig. 118] shows a cross-section of the Allen gearless differential. The main gearing is bolted to the casing. The wheel shafts are splined to ratchet rings. The two lugs of the pawl block are secured in slots in the casing so that the block turns with it. Eight pawls on the pawl block drive, the ratchet rings two on each side operate for forward, and two on each side for reverse. The pawls permit either ratchet ring to overrun them and move freely in the direction of motion, so long as it is moving faster than the pawl block. The lugs of the pawl block have a little motion, about 3⁄16″, in the slots, so that the casing moves this distance before engaging them for forward or reverse motion. This operates the rocking cams by their heads inserted in slots in right angles to the lugs, having the effect of pressing on and disengaging the forward or reverse pawls according to the direction of the motion.
When the car is running by its momentum with the clutch out, the action is reversed and the ratchet rings drive the casing and driving gear through the pawl block.
The adjustment given above also applies to the setting of the Allen differential.
Lubrication.—See Chapter on [Axles].