halfshaft

A halfshaft, also called an axle shaft, is a drive shaft that transmits torque from the differential or transaxle to a wheel. In most passenger cars with front-wheel drive or all-wheel drive, each side uses a halfshaft on the front wheel; the halfshaft is paired with the other side’s shaft to form a complete axle. It carries torque through constant-velocity joints at each end, allowing the wheel to turn while the suspension moves and the steering angle changes.

The inner CV joint connects to the transaxle or differential, and the outer CV joint connects to the wheel hub. The joints are enclosed by CV boots that retain grease. Common joint types include Rzeppa joints for outer joints and tripod joints for inner joints. The shaft itself is typically steel and varies in diameter and length according to vehicle design.

Common failure modes include torn CV boots leading to grease loss and eventual joint wear, clicking noises during sharp turns (often from the outer joint), vibration, or a broken or severely worn shaft. Replacement of halfshafts or CV joints and boots is a common repair in front-wheel-drive and all-wheel-drive vehicles.

Maintenance involves inspecting boots for cracks, replacing damaged boots, and replenishing grease or replacing the joint as needed. In rear-wheel-drive vehicles with a solid rear axle, the term halfshaft is less applicable; those vehicles use a full-length drive shaft to the rear wheels.

Overall, the halfshaft is a critical link in the drivetrain that enables power delivery to the wheels while accommodating steering and suspension movement.