Air Locker Pressures

Recently, our engineering staff has been doing significant testing emphasizing extreme hardcore use and abuse of Air Lockers with the goal of improving durability of wearing components such as the locking clutch gear. We’ve learned that there are a few relatively simple steps that can lengthen times between servicing and rebuilding the diffs.

Let’s start at the basics:

An Air Locker requires a certain amount of air pressure and volume to engage. The clutch gear begins to engage when the pressure of the return springs are overcome by the air’s pressure. This begins occurring around 40 psi.

Our air compressors utilize a pressure switch that fills the tank to 100 psi and turns the compressor back on when it senses a drop below 70 psi. This ensures that there is always enough pressure to maintain a lock, until the Air Locker is disengaged. When the user turns the switch off, the solenoid on the compressor releases the air out the exhaust port. The return springs then move the clutch gear away from the side gear, allowing the locker to then function as an open carrier.

We are often asked, “What pressure can the Air Locker handle?” There is not a single, uniform answer for this question. Each component has a different rating. The blue airline we use is rated to 300 psi. The Air Locker itself can take much more pressure than this (over 600 psi). The solenoid will begin to leak at around 160 psi.

And now the technical stuff:

Testing has shown that using an undersize air source can lead to a pressure drop on engagement which drops below the locking threshold of the units. When this happens, the compressor turns on and slowly runs up to pressure while trying to engage the clutch gears in the diffs and often results in a binding situation and partial engagement. Bound up, the loads inside the diff can exceed the material holding power of the partially engaged clutch gear and cause extremely rapid wear and eventual loss of locking ability. For this reason, higher pressure and capacity are key if you are running a custom air supply. This scenario is very unlikely in a typical trail truck given the methodical nature of operating lockers in that environment, but can easily happen in the timed competition environment.

For the average user, the bulkhead fitting could be the greatest potential for a pressure bottleneck. It is easy to over-tighten the compression fitting and crush the copper seal housing line, thus starving the locker of the quick burst of air.

IF you want to have the fastest engagement possible, you could do what many competition teams have done and move to using air toggle switches. This allows them to eliminate the solenoid and run very high pressures. Air toggles are typically rated at 250 psi and can easily be coupled with a high pressure tank system.