Jargon Buster

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Jargon Buster


A differential is a collection of gears that splits engine torque from the central tailshaft of a vehicle to the two perpendicular axles that lead to the wheels, allowing each to rotate at different speeds.

A differential can be found between the driving wheels on almost all modern vehicles, with many all-wheel drive and four wheel drive vehicles employing up to three (front, centre and rear).

There are many mechanical variations on the differential, but all deliver the same basic operation.

For more on differentials, see Limited Slip Differentials.


A limited slip differential is a collection of gears, clutches and springs or a viscous coupling that splits engine power from the central tailshaft of a vehicle to the two perpendicular axles driving the wheels, allowing each to rotate at different speeds.

If a vehicle was only ever to drive in a straight line on a flat road and never lose traction, then there would be no need for anything but a fixed axle assembly. The reality is however that roads are not always straight, flat or even, surface conditions change and the stresses imposed on a vehicle change by the second, according to the forces of acceleration, braking, cornering and more.

In their most common form, limited slip diffs employ mechanically driven clutches and gears to slow the rotation of wheels under less load (eg. those that have lost traction) transferring that power to those wheels under more load (eg. those that have maintained traction) thus ensuring all available power is being maximised.


A commonly found and easily overlooked problem in modified performance vehicles is a damaged diff housing. While the sharp and sudden impact from a collision will send owners crawling all over their vehicles looking for macro damage, it's the silent, near invisible micro damage that results from excessive weight, heat or stress on your housing that can easily be missed. When damage invisible to the eye can result in leaking seals, shortened bearing life, pinched axle shafts, misalignment and more, it's easy to go spending your hard earned on fixing the symptoms rather than the cause.

Ozdiff employs specialised state-of-the-art diff straightening machinery to accurately measure and straighten damaged diff housings; in many cases returning them to their optimal shape without the use of heat. If you suspect your housing may be need straightening, contact us to arrange an inspection from one of our performance diff experts.

During cornering, a vehicle outer wheels must travel further than its inner wheels, while bearing the increased load imposed by the vehicle's body roll (away from the corner). Without a LSD, the reduced load on the inner wheels may result in inner wheel spin. With a LSD the inner wheel's rotation is retarded and power transferred to the outer wheel driving it around the corner.


Gear lapping is a fine grade finishing process in which a gear set is reshaped and meshed together with an abrasive compound, whilst under pressure. As the lapping process truly mates the gear set's profile by removing and refining its contact surface, lapped gears generally exhibit a high quality finish, increased accuracy, increased strength, a longer life and an improved performance when compared to non-lapped gears.

Gear lapping can also be used to restore and give new life to worn gear sets.