Maxi Trac On-Board Air System - GX470 (1 Viewer)

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Dec 13, 2021
Tucson, AZ

Where to begin…we’ve been relying on a Viair 88p compressor for a while and it worked well (except for the time we had a failure that led to a warranty claim and subsequent replacement, but we won’t get into it). That being said it was:

1) slow
2) could only inflate one wheel at a time
3) took up space in the vehicle when not in use
4) required popping the hood and connecting up to the battery

Because of those reasons, we decided to invest in some kind of on-board air system. Trying to keep to a budget, we picked up a Maxi Trac compressor from NAPA, having heard good things about them and seen similar models favorably reviewed in Australia (Thumper Max). The Maxi Trac cost us $105.33 delivered, although the first one that arrived came with a cracked piece that would have to be sent back for a replacement. NAPA said that due to their supplier process, they could not issue a replacement and instead I had to get a refund and buy a new one. That annoyance out of the way, we started looking around online to see if anyone had mounted one of these under the hood of a GX470 or similar, but there wasn’t much to go on except a couple 4Runners. Before mounting, I decided to take care of a few upgrades to the compressor itself to make it more usable.


Out of the box the Maxi Trac comes with a hose and non-standard air fitting connected to a manifold on the compressor itself. An included hose with pressure gauge can be used to air up one tire at a time, but this defeats the purpose of having a fast compressor. It would be best to be able to inflate all 4 tires at once. I followed the instructions from Kevin Chon’s video on YouTube () to add a pressure cut-off switch and standard air quick-connect fitting to the compressor. I could then easily connect our DIY 4 tire inflation system (several examples on YouTube, just search “diy 4 tire inflation system”).


There are two places where one could realistically mount such a large compressor: in front or behind the airbox on the passenger side. In front of the airbox, you would have to relocate the power steering reservoir, which has been done, but we were looking for a simpler solution. This led us to choose to mount behind the airbox. With that mounting placement there are a couple issues to contend with:

1) the air cleaner hose downstream of the airbox has a resonator with a vacuum line attached that sticks out into the space

2) there is a hardline hose that goes though the firewall that juts up next to the engine and impedes the available space.

We removed the resonator and replaced it with a PVC plug. This plug has a smooth outer surface that mates well with the air intake hose and the end has threads which could be used to connect brass fittings to accept the ~1/8” vacuum line.

These are the specific parts we used:

Here is the result (zip-tie is temporary, although probably not needed due to the nature of the friction fit):

So far so good, no codes from the ECU. With that out of the way, the compressor could comfortably fit (if elevated above the protruding hardline mentioned earlier). Next it was on to the CAD.


I mocked up a rough idea of what we needed with cardboard and painters tape. The bracket had to elevate the mounting location while keeping the top of the compressor low enough to clear the hood. After being sure that the chances of success were over 50%, we decided to cut out some metal. This being my first time welding, I didn’t have high hopes, but I am satisfied with the final product:

For mounting, we took advantage of a factory threaded ground location on the side fender wall and drilled out another vacant hole to accept a rivnut.

For the bottom, I drilled out three more holes in convenient places for more rivnuts. Positioning the bracket in place above the holes (before installing the rivnuts) I went from inside the wheel arch and marked the hole locations on the underside of the bracket.

I then marked the holes for the compressor bolts on the top of the bracket. After drilling out the bracket and installing the rivnuts, I applied rusty metal primer followed by black paint. The bracket gets installed with some plastic spacers to correctly space the bottom on the uneven surface. This is due to the sloping nature of the wheel arch. You can also see in the pictures below the reason why the compressor needs to be elevated and the bracket looks weird.

Finally, the Maxi Trac could go in for the first time. I removed the compressor from the base that it comes with, but kept the rubber isolator feet attached. I then bolted it down using the rivnuts installed earlier. It fit perfectly, just barely clearing the hood and strut when fully closed! The engine cover even fits with some trimming with a Dremel.

Below is a good illustration of why the resonator had to be removed from the air intake hose. Next it was on to the wiring.


When it came to the wiring, I had a couple requirements:

1) easily removable/disconnectable
2) switchable power from inside the truck
3) clean/simple with circuit breaker

To make it removable, I used an Anderson connector. The quoted current for the Maxi Trac is 90A, which is quite a lot so I opted for the 175A Anderson connector and 4awg wire. This is probably overkill, but would rather oversize than undersize. Power from the battery goes to a 120A circuit breaker before feeding a 200A 12V relay and finally powering the compressor. The relay is controlled by our Auxbeam 8 gang switch panel. This allows the compressor to remain switched on at all times, but only powered once the relay is closed. This will make more sense after this next part.


To save the effort of having to pop the hood every time we wanted to air up, I decided it would be best to have exterior access to the air. This meant running an airline out to a chuck somewhere convenient yet out of the way. I settled on the bottom part of the bumper, mounted to the crash bar. This is a perfect spot to connect up our DIY 4-tire inflation system: easily accessible yet protected from damage while offroad. The chuck can be plugged with a clever fitting from Wits’ End (Quick Connect Air Coupler Pacifier -

All-in-all, the system works great. The compressor is solidly mounted, can be switched on from inside the car, cuts off once pressurized, and turns on when needed to fill the tires. Please reach out with questions, comments, suggestions etc. Have a great day!





Not sure why those few pictures are in there twice and can't edit...whoops. Anyway, will update the post once I have the ability to do so.
Nice writeup and looks like a great value!

Roughly how much time does it take to inflate a tire, say from 15 psi to 32 psi? I'm currently using a 20V cordless hand-held compressor and am in the 4-5 minutes per tire realm. Half that would be really nice because having to wait 20 minutes at the end of a trip gets a bit old :).
It is quite large and heavy, but with size comes displacement. Here is one report from the facebook group "2:30 seconds from 15psi to 32psi. 37x12.50r17." and that is on a 4 tire system. Lots of activity on the fb group and youtube where I am sure you can watch a realtime stopwatch if you want.

Someone else on the fb group (maybe here too?) mounted one horizontally in the same area in their 470, but people aren't sure on longevity running it sideways yet even though it is an oil-less system.
Nice writeup and looks like a great value!

Roughly how much time does it take to inflate a tire, say from 15 psi to 32 psi? I'm currently using a 20V cordless hand-held compressor and am in the 4-5 minutes per tire realm. Half that would be really nice because having to wait 20 minutes at the end of a trip gets a bit old :).
Just did a quick driveway test. Keep in mind I’m still rolling on 265/65/R17s, but they aired up from 15 to 35psi in about 2 mins 20 seconds. Not bad at all!
I recently bought a maxi-trac compressor and will eventually mount it under the hood of my 04 GX. Love what you did here but my Aux battery sits behind the airbox... so I will likely be relocating the PS reservoir and mounting in front of the airbox.
Having the spare on my bumper has created a ton of space under the back of the vehicle (should be cooler under there also), I'm thinking of mounting it there and running a hard air line out to a convenient spot to plug into.
Having the spare on my bumper has created a ton of space under the back of the vehicle (should be cooler under there also), I'm thinking of mounting it there and running a hard air line out to a convenient spot to plug into.
That is a great option. Just have to be mindful of the wire gauge if powering the compressor from the main starter battery. There’s even a video on YouTube of a guy mounting his spare battery in that area. I’ll post a reply if I can find it.
I would suggest against mounting a lower-end compressor like a MaxiTrac under the vehicle. I have a lower-end compressor myself (Smittybilt 2781) and from opening it up and modifying it, they really aren't built to be exposed to water, mud, dust, etc, especially in a climate like Louisiana. They are designed to be kept inside a vehicle in a bag, taken out when used, and then put back inside. My Smittybilt had some wire nuts inside of it that I ended up replacing with heat-shrink connectors. The electrical components didn't appear to be waterproof or even water-resistant. They really don't have much of an air filter either, and sucking in some debris could ruin the piston seal (which is a rubber-like material) Also, as mentioned above, you'd have a really long wire run from the battery to the rear, and would need a thick wire gauge.

Underhood is a much better option for a cheap compressor as it is much better protected from the elements. My Smittybilt is mounted behind the air intake box and has stayed nice and dry/clean despite quite a bit of dusty offroading. I also have the QD air connector mounted under the hood, and can quickly access all 4 wheels with a 25' long coiled nylon hose.

If you do want an externally-mounted compressor, perhaps look into a different brand/type that is better suited for element exposure.
@BlizzardtheGX - How is this setup holding up?
Its holding up well with one exception: The standard Flexzilla hose (that runs from the compressor to the air chuck in the bumper) was melting at the output of the compressor after extended use. The solution was to replace the standard Flexzilla air hose with a high pressure braided stainless steel hose. With the correct fittings on the end, the stainless hose was a straight swap with the green Flexzilla hose and has performed perfectly ever since! The stainless steel hose is rated up to 400 deg F and 300 PSI. I have not noticed a performance decrease in using the 4' length of stainless steel hose instead of the Flexzilla.

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