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What is a live axle and what is a dead axle?

Axles are also an essential component of an automobile. There are two types of axles: The one which transmits power to the wheel is known as live axle and the one which does not transfer any power and acts like a beam is known as a dead axle.

What are live axles and dead axles, and their role in an automobile?

Axles are an important component of a car. All cars have two main axles in it: front axle and dead axle. Apart from this, there is a stub axle which is not found in every car. Axles are a kind of shaft which freely rotates on its desired axes, the axes connecting centres of opposite side of wheels. Axles are used to rotate the wheels of a car. Sometimes, other mechanical components are also mounted on axles.

The main forces acting on an axle are as follows.
• The weight of a body
• Driving thrust
• Torque reaction
• Side Thrust

Apart from the front and rear axles, there are two more types of axles that are live axle and dead axle.

Live axle

Ford 9" Live Axle
Courtesy: Car Throttle

Live axle transmits power to wheels coming from the differential. Or a mechanical engineer will call it a ‘prime mover’.

The live axle is in a two half axles both of which are combined with a differential using the universal joint. Each half of a joint is connected to its corresponding wheels using constant velocity joint (CV). The role of CV joint is to facilitate vertical as well as pivot motions of a wheel assembly.

Dead axle

 

 

The dead axle is also known as a lazy axle.The dead axle is not a working part of a drivetrain but is actually on the drivetrain. It is not responsible for the motion of a car as it doesn’t transfer any power to wheels. Instead, it is just a freely rotating axle used to mount bearings, wheels sometimes even gears. No differential or driveshaft is attached or connected with it.

So which one is live and which one is dead axle out of two axles: Front and rear

Well, it depends on the configuration of the car. In an RWD car, the rear axle is a live axle and front axle is a dead axle. While in an FWD car it is inverse that is front axle is a live axle and rear axle is the dead axle. Then what about AWD cars? Yes, they do not have a dead axle, both the axles of this type of configuration transmit majority or minority of power so both of it is called as a live axle.

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