There are many components that work together to produce the motion of a car. One of these components is the axle. The axle is perhaps one of the most important parts on any type of transportation vehicle. An axles job is simply put, to allow rotational movement between two wheels, while allowing them to move freely along an axis at right angles to them. All the power of the engine gets transmitted through this simple connection and it has to be rugged enough to take all that punishment without separating or breaking (and little does).
An axle consists mainly of four main parts; A metal housing containing some gears and bearings, an end cap that holds everything in place on each end, grease for lubrication and some means by which power can be transferred from the engine to the axle.
The bearings that reside in the housing, allow it and therefore all parts attached, to spin smoothly along an axis at right angles to its length whilst keeping everything as straight as possible. The end cap is what keeps everything secure and together, and must be able to stop all axial movement should anything go wrong with any of these internal components (which can be costly). The grease helps keep the bearing lubricated, allowing them to spin freely without causing friction which would cause heat and wear on those expensive little bearings. Finally the means by which power transfer occurs (usually via a driveshaft) can vary greatly depending on how many wheels need moving or if they are static or not (we will talk about this in another article). Usually the power is transferred to the axle via a serpentine belt or in newer vehicles with independent suspensions, electric motors for each wheel.
If the bearings get too hot from excess friction, they will expand and seize up. This can cause serious damage to all components involved and make for some expensive repairs. Grease on the other hand keeps these parts lubricated, but it also gets thrown off due to heat and causes its own problems where it has been thrown around inside an axle by spinning wheels (such as into bearings causing them to seize), or between gears which then causes excessive wear of those parts.
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