To appreciate the value of the selective drive attachment, it is necessary to fully understand the operation of the standard front wheel drive unit.  Power, generated by the engine, is transmitted through the clutch, the standard transmission and the transfer case to the front and rear axle differentials.  In the transfer case, the 4-Wheel Drive selector lever couples forward drive shaft to the gear train that is driving the rear differential.

The front wheels, with the standard hub, are directly and permanently connected to the short spline shaft marked "A" in the illustration. This spline shaft is permanently connected to the constant velocity ball joint (B) which in turn is permanently connected to the axle (C), driven by the front differential (D). The front differential is directly coupled to the forward drive shaft (E), the rear end of which turns freely in its housing if not in 4-Wheel Drive transfer case.

Thus we see that although 4-Wheel Drive is not desired, the front wheels, because of their direct coupling to the front end of the power train, turn all of the elements that are used to furnish 4-Wheel Drive power without any benefit derived therefrom. The Selective Drive hubs have, as their function, the freeing of the front wheels from their permanent connection with the forward end of the power train and, by so doing, prevent the front wheels from making all of these elements rotate. The advantages of such a selective drive device are readily seen. They are: a ) the reduction of wear on the front end axle shafts, differential gears, ring gear and pinion, constant velocity ball joints and drive shaft when the vehicle is used in 2-Wheel Drive; b) in the reduction of wear on the tires; c) easier steering; d) increased gas mileage; e) longer coasting, etc.

There are two (2) factory-approved models of the selective drive hub. They are: 1) fully automatic Model WA-1,and 2) the manual locking hub, Model WL-2.

MODEL WA-1 AUTOMATIC

This model automatically disengages the front wheels from the forward power train in all standard transmission gear selections including reverse in high range. Thus, in 2 -Wheel Drive operation with all of its advantages, the front end drive is completely disengaged. When 4-Wheel Drive is needed this selective drive hub automatically couples the front wheels to the front power train, in all forward speeds giving traction on all four wheels. This automatic operation is performed when the selective drive hub is set in the "Free" position. The only occasion for locking this model is when 4-Wheel Drive reverse travel is desired. It is useful to think of this selective drive hub as a miniature overdrive system which automatically engages or disengages the front wheel from the forward power train when the conditions require it to do so.