Live axle

A live axle is a type of transmission to a set of wheels in which the drive components (shafts, gears, etc) are part of the suspension and move with it. Until the 1980s it was the most common form of driving axle found in the average rear-wheel drive car.

A typical live axle consists of a solid tube with a central casing containing the differential, with the wheels mounted on each end of the tube. The drive shafts run inside the tubes. The whole assembly is connected to the vehicle body or chassis by links and springs. Because the axle follows the road, with the vehicle body moving above it, drive is supplied to the axle via a swinging propellor shaft and universal joints. While relatively cheap to manufacture due to its simplicity, its weight (which is part of a vehicle's unsprung weight) can lead to handling problems.

Live axles are still widely used on trucks and heavier vehicles, but in cars they have mostly been replaced with front-wheel drive or independent rear suspension (IRS) designs.