What is a differential?

What Is a Differential?

In simple terms, a differential on a vehicle allows power to be fully used by a set of wheels connected to the power source such as a drive-line.  Let’s discuss different drive or powertrain configurations. 

  1. The simplest powertrain is an axle with a wheel attached to each side; the axle being a solid shaft. Rotary power is given to the axle.  The result is that both wheels turn at the same time.  Remember that old gas-motor go-cart in your Dad’s shed . . . with one of the rear wheels always worn out or with no traction.  When going in a straight line, there is no problem with the wheels, in fact this is an ideal situation for power optimization.  However, upon turning left or right, one wheel respectively, must slow down (i.e. turn less) or risk skidding on the ground, or not turning at all; hence tractors with left and right brake pedals, bulldozers with steering clutches, etc.  See the youtube videos below.
  2. To solve the problem in number 1, a split axle was developed. The wheels still had an axle attached to them, but approximately in the middle a section was cut out.  Gears were machined and placed on the cutoff ends. A special gear assembly, perpendicular to the axles was placed so that each axle could spin at different speeds of each other when on a curve, but work with equal spin when advancing in a straight line.  The same amount of power is given to the wheels.  When a vehicle turns though, the power is divided between the 2 axles given the amount of turn.  This constitutes a simple differential.

But why bore you with words when you can see a differential in action on youtube.  There are several videos related to this topic which are well explained in presentations and example. 

Try these videos: