Alloy Steel

Steel containing significant amounts of elements (besides carbon and certain amounts of trace elements) added to change the mechanical or physical properties of the steel. Specifically, steel is considered an alloy when it contains more than the percentages listed of one or more of the following elements: 1.25 percent manganese, 0.60 percent silicon, 0.60 percent copper, more than 3.99 percent cobalt, columbium, molybdenum, nickel titanium, tungsten, vanadium, zirconium or any other alloying element.


If the steel becomes too hard, it can be softened, or annealed, to a desirable hardness. This is done by heating to a predetermined point (according to the material) followed by a slow cooling. This process is also used to relieve the internal stresses in a part.

Axle Hop

See Axle Wrap

Axle Shaft

The forged steel bar that connects the differential to the wheels. It transmits torque from the differential to the wheel and may also support the weight of the vehicle.

Axle Wrap

Torque and traction combine to twist the axle (pushing the nose of the differential up and going forward and down going backward) by twisting the leaf spring into an “S” shape. The energy is stored in the spring until the tire slips, and at that point the spring snaps back violently. Sometimes this results in a hopping sensation, hence the other common term, “axle hop”. It can be very hard on driveshafts and u-joints.