The Differential Lock

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This piece of equipment is in many cases a game changer when off-road and you get stuck. Commonly known to off-roaders as a “locker” the differential lock or diff-lock is a variation of a standard open differential. An axle has two drive shafts joined to the differential that are driven by the differentials gears. This allows wheels to rotate at different speeds when turning around corners. The open diff provides the same torque (twisting or rotational force) to each wheel. The gearing allows a different rotational speed. In other words in a left hand turn the differential will slow down the left hand rear wheel allowing the right hand outside wheel which has less traction to cover the greater radius. This also stops what is known as tyre scrubbing or scuffing.

This is however a drawback off-road, when the loss of traction to a wheel is sensed more rotational speed is directed to that wheel causing it to spin – at this point you are generally stuck.

That’s when the diff-lock comes to play; it overcomes this limitation by locking both wheels, allowing them to turn together regardless of the traction lost. This generally allows the wheel with traction to pull you through the obstacle.

Engagement may be electronic, pneumatic or hydraulic. As a rule you will engage the locker before entering the obstacle if you were able to correctly assess the situation.

The same principle applies to lockers fitted to front and rear axles as well as the centre lockers fitted to a full-time 4WD vehicle.In this case, the open centre diff prevents “wind up” between the front and rear axles ,it will be engaged  when the vehicle goes off-road.

Differential lockers are fitted as original equipment (OE) by most manufacturers. A switch fitted on the dash or centre console engages them. The benefits are better drivability, with the on demand locking capability. However one will put the drive train components and tyres under tremendous strain if you leave a diff-lock on and drive on a hard surface. A diff-lock is very useful when axle articulation is limited in the case of vehicles with independent suspension.

 

 

About the Author
Glyn Demmer

Glyn Demmer

My first 4x4 was a Nissan Hardbody thereafter I started travelling all over the country. In 1992 we held a big 4x4 day with hundreds of Nissan families, and then the 4x4 bug really bit. A friend Monty Brett and I started running 4x4 courses at the Hennops Off-road Trail just outside of Johannesburg. At first we offered day-and-a-half courses that started on Friday afternoon and finished on Saturday afternoon. Hannes Grobler the Rally Ace regularly assisted, and we reached a nice balance between our two styles and our skills.

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