Using CO2 For Your Locker

Use a CO2 tank to operate your ARB locking differentials!

May. 01, 2006 By Matthew E. Stocke

By a huge margin, the number one question I get asked when people see my Jeep for the first time is: “what is that tank in the back”? The tank is, of course a compressed liquid CO2 tank. But it can be used for so much more than just filling your tires. Read on……

For those not familiar, 4-wheelers often use a portable CO2 tank to fill their tires after off-roading. Tire pressure is lowered while off-roading for better traction. A small air tank will not hold enough for even one set of tires because it is only about 100PSI. But a CO2 tank is liquid at 2000PSI (approximately); giving loads more volume as it exits the tank compared to air only. Another additional benefit is that the tank will operate air powered tools. I actually used my tank extensively to power an air nail gun when installing trim in my house. What I’ll explain here is yet another great use for that same bottle.

ARB’s are locking differentials which you can turn on or off using compressed air (90PSI). The typical installation of ARB’s includes solenoids, switches, a compressor, and possibly a small air tank. I didn’t want all of that complication, so I found out a much simpler (and less expensive way) to run my ARB’s using the compressed air out of my CO2 tank. I did the installation in a CJ7, but really the parts and installation could be adapted to any vehicle. Here we go!

Parts List

You will need the following items, or something equivalent (I have also noted where I bought each item and the cost):

  • 10 lb CO2 tank, new aluminum with protective handle: Ebay $80
  • (any size tank from 2.5lb on up will do for ARB duty, but for tire filling, 10lb and up is recommended)
  • 90PSI Regulator: Williams Balloons $40 (a regulator which allows you to vary the output pressure could also be used and is available and any welding supply store)
  • Air line quick connects: hardware store $8
  • 3/16” air line: Grainger $8 for 100ft
  • Pneumatic switches: Campbell Enterprises $70 (also available via Grainger-type stores)
  • Various Prestolok type fittings and brass fittings: Grainger $20
  • 10lb fire extinguisher bracket: Grainger $35
  • Coiled air hose 20ft: clearance at (you can find them on Ebay pretty cheap too, but make sure you get urethane to handle the cold air coming out of the tank, not the nylon ones which cannot handle the cold CO2 gas coming out of the tank)
  • Air chuck: hardware store $3

The basic layout:

The CO2 can fill tires OR run the ARB’s, but never both at the same time. There is a quick connect air fitting after the regulator so you can disconnect the pressure to the ARB’s, or hook up a coiled air hose to the tank and fill tires. This is where an adjustable regulator would be useful. I used a fixed 90PSI regulator, but if you had an adjustable regulator, you could increase the pressure to fill tires quicker (I like the simplicity and small size of fixed regulator). One note: if you run a pressure any higher than 99PSI static (not flowing) to the axles, the ARB seals could burst (according to ARB). Keep this in mind if you use an adjustable regulator. You do not need to buy a unique CO2 tank for this setup, you can just as easily use any of the CO2 systems out there on the Jeep market for tire filling, but to prevent damage, the ARB operating pressure should operate at 90PSI.


From left to right:

  • Coiled air hose with air chuck and quick disconnects on either end.
  • Below that are the pneumatic switches (clear hose to CO2, blue hoses to axles).
  • Next is the regulator with quick disconnects,
  • the CO2 tank, and
  • finally the tank bracket.

Mounting the CO2 tank:

I mounted the tank in the back using a fire extinguisher mount from my local fire prevention supply store (look in the yellow pages for your local one). It fits just right behind the rear seat. Remember that the tank must be top up (not laying flat on it’s side), because you want the CO2 gas to come out, not the liquid (that would be bad).

The fire extinguisher mount, which holds the tank, is bolted to the side of the fenderwell. Powertank has some super cool mounts for various mounting styles too. A 3 rd option are tuber mounts from the company Quickfist.

Connecting the fittings at the tank:

Connect all of the fittings as shown in the pictures. (Note: in the photo, the quick connect valve at the tank, and the regulator are already screwed together). The valve on top the CO2 tank should be closed unless you are wheeling; this way there will be no minor leaking of the CO2 while the jeep is parked. When you flip the pneumatic switch to either the front or the rear, air pressure (at 90PSI in this case) goes to the ARB, locking your axle 100%. It’s that simple. And when you turn the switch off, the switch vents the line from the ARB, releasing pressure to atmosphere and unlocking the differential (very handy on hard surfaces in 4wd when turning). When choosing your pneumatic switch, make sure you use the venting type (I have been told that there are different types). One huge advantage to this whole setup is the ability to use SAE size hose (more readily available in USA) instead of the metric ARB. That, and of course, no electricity, wiring, pumps, or permanent mount tanks are required.

Close-up of the connections from tank to switches / air hose

Air line connections and switch installation:

The Prestolok type fittings are treaded directly into the switches. These fittings are GREAT! You simply push the air hose into the hole and them make an airtight seal (the harder you pull, the tighter it stays in). To remove, pull back the collar, and pull on the air line in the opposite direction. These fittings replace the multiple part brass compression fittings I have had to use in the past (and which come with the ARB unit). I used the Prestolok at the axle and discarded the ARB compression fittings. Straight couplers can even be kept on board as a trail repair in the instance of a cut airline!

The Prestolok type airline fittings

Close-up of the 2 pneumatic switches setup with all fitting mocked up prior to installation. On the top is the single air inlet, then air out from each switch to each axle.

I used 3/16” air line from the tank to the switches. The air line runs along the floor from the tank into the back of the switches. I also used the 3/16” from the switches to the axles. This sounds small, but the ARB’s don’t need much air volume at all, mostly pressure. Be careful not to run too tight of a bend in the hose or it will kink (kind of like stepping on a water hose: -it will block the air flow). Tie the air lines out of the way under the vehicle as much as possible. If you have extended breathers, you can tie-wrap this air line right next to them for protection.

Since I do not have a radio, there was a perfect open spot in my Tuffy console for switch placement. I made a small cardboard template, and mounted the hose and switches to the panel first. Then I fabricated a small panel out of 3/16” aluminum plate patterned off the cardboard. I used a small bit of silicone to hold the small panel in place in the console. The setup is the ultimate in simplicity and you retain independent control of the front and rear lockers.

Mockup of the switch panel made of cardboard

Rear side of the cardboard mockup panel with all connections made.

ote the switch vent, which is made of sintered brass to vent air, but protect the switch from debris.

Final installed switch panel, mounted to the console with silicone.

Here the two clear hoses coming from the switches in the console coming through a small hole in the floor heading out to each axle. A small bit of silicone was used to seal the hole.

Here is another switch mounting example in a dashboard. This is a rock buggy dash (I took this picture at the SEMA show). This particular buggy used a tiny paint gun size tank since it only runs the ARB’s.

So how much CO2 will I use up?
At SEMA, Don Campbell at the Currie booth told me that a 2.5lb tank would operate a pair of ARB’s for a whole summer, wheeling every other weekend. In reality the ARB’s use hardly any volume at all. But of course filling up your tires will use up the tank much quicker. A 10lb tank will (approximately) inflate a set of 33"x12.50"x15" tires from 10 to 25 PSI - 8 times. I refilled my tank 2 times during the first summer of wheeling. This included some airing up the tires, and many on and offs of the ARB’s.

A 10lb CO2 refill will cost you about $12 at my local welding supply store (prices vary across the country). Remember to tell the store filling your tank that you want YOUR tank back (if you care), because many locations simply swap them out for a full one, and you are stuck with some old random tank.

So that’s it, very simple, and serves multiple purposes. As a bonus the little black knobbed switches look pretty cool. Thanks to Don Campbell and all the other rockcrawler guys I met in Las Vegas at the SEMA show. A few of them had done this, and that’s where I got the detailed information to do this. In my case, this project was combined with my axle swap on my CJ7, but this could easily apply to anyone who has, or is considering one or a pair of ARB lockers! To some of you this may be old news, but this setup to me is the best thing since sliced bread!

Here are some useful links to help you complete YOUR project:

A few additional notes: Feel free to email me at for questions or pictures you would like me to take for you. I received no free products or services from anyone when completing this write-up. EVERY Jeep is different (even one right behind the other coming off the assembly line), so keep that in mind that what did work for someone else might not exactly be the best solution for you (and the other way around). These articles are my opinion based on my experience. Don’t send me hate mail if you don’t agree. Do all of this work at your OWN risk. I am not responsible if you don’t know what you are doing and you hurt yourself in any way. Newsletter
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