Whether you're pulling your boat out at the boat ramp, spinning wheels in the sand or getting wheels in the air off-road, your 4wd's diff-lock is your new best friend.

What is a diff and why do cars have it?

The name, "diff", is short for "differential". The diff's main task is to assist your car when cornering. As a car turns a corner, the left and right wheels have to travel different distances. As a result, the left and right wheels have to spin at different speeds. The easiest way for the diff to achieve this is by disengaging power to one wheel and simply powering the easiest side. This side is called, the wheel of least resistance. In day-to-day driving, this offers less wear and tear on your vehicle and roads, better handling and a smoother ride.

So why are diffs bad off-road?

For 99 per cent of your off-road driving, your diff will be great. You will make tighter turns and put less labour on your engine. But every now and then, it will work against you. When driving off-road it is not unusual to find yourself without traction. This could be because of slippery mud or boat ramps, soft sand, or even from having a wheel in the air. It is at this point that most people have to get and spend time packing things under their spinning wheel. What is happening, is that your diff is recognising the wheel without traction, as the wheel of least (or in this case no) traction. As a consequence, it is getting all of the power diverted to it, while the one with traction, sits still.

If you're lucky enough to find yourself in this situation, but with a diff-lock available, don't get out with your shovel and start to sweat. Simply press this magical addition and feel it go to work. A diff-lock does exactly what it says on the box; it locks the diff. By over-riding the diff's natural function, your car is able to push power through to both wheels and drive until they both have traction.

This means more time enjoying the view from air-conditioned luxury and less time recovering stuck vehicles. So next time you find yourself in this situation, smile, knowing that you invested in a diff-lock.