28th January, 2011

Dear ARB,
I was wondering what is the best option for an ARB diff lock if I was only going to get one front or rear? I do most of my driving in bush and have had cross axle traction problems so I was hoping a diff lock would solve a bit of my problems.



Unfortunately the question of front vs rear is always going to come down to operator opinion. It is a subject that has been heatedly argued around campfires for decades.

ARB does not specifically recommend one axle over another for your first Air Locker, as even our own staff do not all share the same preference. What we can offer you though, are a few good points to consider when making your own choice:

1. Generally, you will always have one front and one rear wheel firmly on the ground. So to a great extent, significant traction will be added by locking either axle. The amount of traction available to a locked axle increases with the amount of weight on it. So, if you tend to carry a lot more weight in the rear of the vehicle, more traction will be offered by a rear Air Locker. Similarly, if you drive a ute or cab chassis that is most often unloaded, then you would stand to gain more traction from locking the front, as the bulk of the vehicles weight is being carried by the front axle.

2. The uphill incline of a vehicle can greatly shift weight to the rear axle, and as we mentioned above, more weight at the rear axle means more traction if its fitted with an ARB Air Locker. When a vehicle travels downhill and its weight is transferred forward, a rear Air Locker can also be of benefit. On downhill descents a vehicle with an open diff can experience a sliding effect as drive transfers from one axle to the other. A rear Air Locker will counteract this motion giving more control and a safer, slowed descent.

3. A vehicle will steer better with only the rear axle locked than it would with only the front axle locked. The advantages of the bonus traction most often far outweigh the disadvantages of understeer, but generally you will usually find no noticeable understeer as a result of only having a rear Air Locker engaged.

4. Limited slip differentials (LSDs) can help a little. If youre only going to buy one Air Locker at this time, and you put it into the front of a vehicle which is factory equipped with a rear LSD, then youll have maximum traction at the front, while still retaining a little traction in the rear.

5. Rear differentials tend to be bigger than front differentials (although this is not always the case). An ARB Air Locker is going to effectively DOUBLE the maximum amount of traction that was offered by your factory equipped open differentials. If you are only going to install an Air Locker into one axle then it would make sense to put it in the biggest and therefore strongest axle in the vehicle.

6. Your front wheels get over the crest of a hill before you do. A steeply inclined surface offers very little traction compared to a level surface. Having your front wheels over the crest of the hill onto the level ground does not always guarantee that youll get the back wheels over as well, but in this situation, an Air Locker in the front may just pull your vehicle up and over the crest.

Consider these points carefully when choosing. Different vehicles and the preference given by their drivers are always going to have an effect on the final conclusion. What we can definitely conclude is that having an Air Locker fitted to both axles would offer you the best of all the situations above, and the maximum amount of off road traction that is physically possible to get from your vehicle.

Daniel Bongard
(Engineering Supervisor)