Frequently Asked Questions

Q: In my vehicle, the diff lock automatically comes in when in low ratio, and a push button for high ratio. I don’t believe that this gives me individual traction on the four wheels. Could you please explain the difference between diff locks (as above) and the ARB Air Lockers?

A: The ‘diff lock’ you are referring to is not an axle differential lock like an ARB Air Locker, but rather what is correctly referred to as a ‘centre diff lock’. It is a very common misconception that they are the same thing, when in fact they are quite different in function and benefit.

The centre diff lock you have serves a similar purpose to ARB’s Air Locker except that a centre diff is there to ensure equal traction between your front and rear axles only. All traction losses from side to side (from left to right wheel across the same axle) are not accounted for at all by a centre diff lock until you add an Air Locker to one (or both) of your axles.

Note: A centre diff is not even included on most part-time 4WD vehicles (i.e. vehicles with manual front hubs) and therefore their centre is always locked.

Here are a few examples:

• Have you ever noticed that if you turn off your centre diff lock your vehicle will spin its front axle as you climb up a steep hill? This happens because most of your vehicle’s weight is bearing on the rear axle while climbing uphill. A locked centre diff will save you from losing this traction from the front axle.
• Have you ever noticed how 2WD vehicles pulling a boat out of the water on a slippery ramp will usually spin the right hand tire? This is from torque bias caused by the torque from the vehicle’s drive shaft, and is remedied when you turn an Air Locker on as both wheels are forced to spin at the same speed.
• Have you ever brought the whole vehicle to a halt just because one side of the track is slippery (e.g. from mud)? Without an Air Locker, a traction loss on one side of the vehicle equals a traction loss on both sides. Locking an ARB Air Locker will save you from losing traction on the side of the track that still has a good surface, and most of the time this is enough to keep you going.
• Have you ever brought the whole vehicle to a halt as you attempt to climb over a bump on only one side of the car? You will find that this occurs when the tire that is NOT elevated on the bump loses traction and spins. This happens because the other elevated wheel is lifting the vehicle upward and reducing the down force on the opposite wheel. A locked Air Locker will never allow one wheel to spin freely – even if it is hanging in mid-air.
• Have you ever found it difficult to steer when driving up or down steep hills? This happens because of varying traction conditions on different tires which allows one side of the car to slip while the other side holds firm. The spontaneous steering effect that results can dangerously get you sideways at the worst possible time. An Air Locker will assist you with steep ascents and descents as it will maintain an equal rotation on all locked wheels, which has a natural tendency to track the vehicle straight, thus preventing your vehicle from yawing from side to side as the road surface conditions change.

Hopefully company reply has clarified the difference between centre diff locks and axle diff locks like ARB’s Air Locker. You should also be aware that because the locations of the centre diff lock and Air Locker axle diff locks are totally different, you are always able to add an axle diff lock (or two) onto your axles to work together with your centre diff lock, to get the maximum grip available to your vehicle.

Q: 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.

A: 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 their own staff do not all share the same preference. What company can offer you though, are a few good points to consider when making your own choice:

• 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.
• The uphill incline of a vehicle can greatly shift weight to the rear axle, and as company 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.
• 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.
• 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.
• 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.
• 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 brand 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.

An ARB Air Locker can be engaged at any speed as long as both wheels are spinning at the same rate. If one wheel is spinning faster than the other, what is called “crash locking” will occur and can cause damage to the internal gears. They recommend that the vehicle stops and engages the Air Locker before attempting an obstacle.

Fitment of ARB Air Lockers to vehicles fitted with OE locking differentials varies from vehicle to vehicle. Please refer to the Air Locker Application Guide for further details.

ARB strongly recommends the use of a genuine ARB Air Compressor; however, the Air locker can operate on any alternative air source that meets the requirements as stated in our Air Locker fitting instructions.

No, each of their air compressors has provisions to activate 2 (two) Air Lockers i.e., front and rear.

ARB Air Locker service internals vary depending on vehicle usage, terrain, and conditions. Please refer to the Operating and Service Manual and your vehicles owner manual for routine oil changes.

Company off a kit (ALAP) that includes everything you need to plum your compressor to the ARB Air Locker.

Company recommend following your vehicle users manual for the quality and viscosity. They DO NOT suggest any oils with limited-slip additives as they can shorten the life of the ARB Air Locker seals.

The ARB Air Locker will engage at around 70 PSI. However, for faster engagement and disengagement, they recommend an air pressure supply between 100 and 150 PSI.

For further information, please refer to warranty terms and conditions on Warranty Page.

The number one cause of differential oil traveling up the ARB Air Lines is due to differential housing pressure. If the housing does not vent properly, pressure will push the oil up the lines. To remedy this, check to make sure your factory breathers are not clogged or enlarge breather ports/hoses to allow more ventilation. ARB now offers a breather kit (170112) to help remedy axle ventilation problems.