ARB Air Lockers are a very effective additional drive system, and this one is for the dedicated off road enthusiast. In short, it involves replacing the heart of a vehicle's drive system (the differential) with one that is very rugged, very well engineered, simplicity in use, and designed to provide the ultimate in traction.

It didn't take me very long once I owned a four wheel drive to realise that the vehicle was not quite the unstoppable beast I thought it might be. I found that in slippery or really rugged off road conditions, despite the best efforts of the four wheel drive and low range, the car would simply lose momentum once a wheel lifted or started to spin badly.

Like all four wheel drives, this is because the vehicle has been manufactured for highway travel conditions. This means that the drive system (via the differentials driving the axles to each wheel) has been programmed to allow wheels to turn independently of each other, which eliminates any binding during turns.

Gears within a factory-fitted differential (the large case we see under the car with the axles coming out of it) are intended to mesh to provide drive but not in a constant state. A certain amount of independence is built in to assist in turns at highway speed.

The factory system is great on road, however, it's somewhat of a hindrance off road. This is because the power when in tough off road conditions often goes to the wheels with the least traction once they start to spin or if they lift off the ground. But there is a solution: introducing ARB Air Lockers to the Rescue.

Without getting into too much technical detail, the Air Lockers work by taking away the ability of the wheels to turn independently by physically locking a specially manufactured differential expressly designed to deliver equal, not intermittent, power to each wheel.

The ARB differential locks the axles, which will then turn the wheels in unison. Therefore, loss of traction off road is very unlikely with the fitted Air Lockers.

This system is strictly for off road; it is not intended for highway work at all. However, the system is simple in operation and it won't detract one bit from highway performance. The ARB diff lock system is only activated when the driver requires extra traction to negotiate a slippery gradient, ice, snow, boggy conditions and the like.

The Air Locker is set up using a ready to use kit, which literally has over 100 configurations available to suit a wide range of vehicles for four wheel and two wheel drive. The kit comprises of very heavy-duty differential components including industrial grade air lines, control switches, and other fittings.

ARB promote the compressed air activated Air Lockers as offering 100% traction to the differential. Advantages include: less momentum needed to overcome a given obstacle, reduced-approach speed making it safer, and a vastly increased traction so the driver can concentrate on the job at hand and take things at a steady pace.

The ARB Air Lockers are activated via a vehicle mounted 12 Volt air compressor set up under the bonnet. The compressed air on hand pneumatically locks the selected diff, or diffs. There are two air compressor options, and the larger one can be fitted to inflate tyres, air mattresses and similar.

Within seconds of activation via a toggle switch the special patented gears within the diff are totally meshed. As the result all slip, even limited slip, is eliminated.

The ARB Air Lockers are only engaged by a driver when actually needed, which means that the vehicle will drive in an entirely standard or factory set up manner at all other times.

ARB will get a qualified differential technician to install the units. When installed with an ARB air compressor the system is supplied as a complete kit with all necessary components. The use of ultra heavy-duty components is standard with the provision of the Air Lockers.

Recently I was a passenger in an ARB Air Locker equipped vehicle being driven in very slippery terrain at Land Cruiser Mountain Park at Jimna in Queensland. This area was the 'Test Track from Hell': a deeply rutted, muddy, and very steep slope and I could not see any chance of success in tackling it successfully.

But of course, once the Lockers were silently engaged the vehicle was transformed from something hard to control to mooching along very sedately without the slightest need for increased power or any trick driving. I went from being bounced around to sitting back taking in the scenery as the Land Cruiser ute climbed the slope in a tractor-like mode.

The Air Lockers really do work and if you are serious about off road capability in really tough going they are well worth the cost of installation.

If you would like to see the lockers in action there's a YouTube clip available on [url=http://www.arb.com.au/interactive/videos] which makes very interesting viewing.