What Is a Half Axle?

A half axle is a component used on an independent suspension and is found in vehicles such as a Corvette, Jaguar XKE or some versions of four-wheel drive trucks. The axle shaft runs from the solidly-mounted axle differential to the wheel or halfway across the suspension, hence the term half axle. Commonly fitted with a universal joint (U joint) or a constant velocity (CV) joint on each end of the half axle, the suspension is allowed to travel as road conditions warrant without binding the suspension. While the use of outboard braking systems is common on trucks, some sports cars and high-performance vehicles rely on an inboard braking system that places the brake disk between the differential and the half axle.

One of the advantages of using the half axle with an independent suspension is the elimination of a great deal of unsprung weight from the drive line. By mounting the axle differential rigidly to the vehicle's chassis, it is not bounced up and down as the vehicle encounters bumps. Only the tires and the half axle are moving in relation to the suspension travel. This creates a vehicle that will recover much sooner from the effects of a bumpy road or race track surface, allowing the vehicle to use more speed and be controlled much easier by the driver.

For a suspension that has extra travel engineered into the axles, a split half axle is often used. The two halves of the axle expand and compress on each other, providing a great deal more suspension travel without creating suspension bind. Commonly relying on a splined shaft being inserted into a splined receiver, this style of axle is able to retain all of the strength of a one-piece axle shaft. Increased maintenance is required with this type of suspension since there are far more U joints to grease and service.

In the world of hot rod and custom vehicles, the use of the independent suspension half axle is commonly adapted to street rods due to the amount of additional chrome the components allow. The Corvette suspension is commonly used in street rods due to its improved geometry and improved ride quality, while the Jag rear suspension has often been called the most beautiful rear suspension ever to be installed in a vehicle by some of the governing bodies of several hot rod clubs and car clubs around the world.