3rd May, 2011


I have two questions for you about Air Lockers. I would like to
know whether they are fact or fiction.
Firstly, I have heard that you shouldn’t install Air Lockers in
full time 4WDs such as the Prado because it will break the
transfer case as only the rear diff is locked and not the front,
causing the transfer case to fail.
Secondly I have heard rumours that there is an O-ring in the
ARB Air Locker that fails, causing the locker not to operate or
drop out if already engaged. Other reports say this has been
rectified. Could you please tell me if this is a problem that
may be experienced or if it has indeed been rectified. I am
considering buying a locker for the rear of my Prado but don’t
want any problems.


Hi Darren,

In regards toyour first question, this is really no more the case than to say that putting better quality tyres on your Prado would be bad for your transfer case. The fact is that an ARB Air Locker differential is a traction aid only, and so it is only the increased traction available to your vehicle with a locker engaged that could ever put your transfer case under more strain than it would be exposed to otherwise.
For example, as you drive up a steep hill that is paved and dry you have a very high level of traction, and your transfer case is therefore under more strain than it would be if that hill were covered in loose gravel and the tyres were slipping. This can also be the case if only one axle or one side of the car happens to be on loose gravel. And with each unlocked slipping wheel, a great deal of your vehicle’s driving torque is lost, as you stray closer and closer to being stuck. The difference that your ARB Air Locker will make to the vehicle is that it will prevent the vehicle from losing its driving torque to every slipping wheel – essentially making gravel behave a lot more like pavement, and that is exactly why you would have one.
And in regards to your second question, although we cannot say that from time to time we have never had an air system failure in an Air Locker differential, what we can say is that this is an extremely rare case, and that it is never the result of simple wear and tear under the conditions of regular use.
The O-ring seals ARB builds into Air Locker differentials actually have a lower wear coefficient than the metal surfaces they run against, and we have seen Air Locker O-rings last in excess of 500,000km and still perform flawlessly. The fact is that when an O-ring fails, you can generally find the culprit very quickly by looking in the direction of particle contamination in the oil from poor maintenance practices, from rust on the sealing surfaces caused by water ingestion due to ineffective axle breathers, or from cumulative damage caused by physical damage done to the sealing surfaces at the time of installation.

So what this means is that we would expect that a properly installed and maintained ARB Air Locker should be able to depend on its original set of seals for the full life of your 4WD.
Daniel Bongard
(Engineering Supervisor)