Strictly, the term ‘rear axle’ refers to the actual shaft connecting the two rear wheels. However, the term is generally used to describe the entire housing unit for the rear wheel connection, suspension and braking systems. One chief function of the rear axle is to deliver torque to the rear wheels. In some (older) cars it is also responsible for ensuring that the rear wheels operate in synchronisation with each other. Modern cars use a split-axle system whereby each wheel is attached to a separate shaft, allowing them to have independent suspension and to be driven at different speeds – useful when cornering. The main advantages of the split-axle system are a smoother ride, better traction and a longer lifespan for the tires. Signs of a rear axle beginning to fail include unstable handling, positive or negative camber on the wheels and knocking noises from the rear.