Rear Differential Breather Relocation

All of the gear boxes on the FJ Cruiser have breather caps on them. The breather cap allows the gear box to release pressure and prevent pressure from being applied to the seals. The breathers can present a problem when submerged.

Fitting on Differential

When a gear box is cooled quickly by water the pressure drops and it attempts to draw air in through the breather cap. The caps are designed to seal when suction is applied but it can be held open by a small grain of dirt. If the breather is open when submerged in water the gear box will draw water in and contaminate the gear oil.

Vacuum T

To prevent the gear box from drawing water in it is best to relocate the breather intake to above the expected water level.  On the 2010 FJ Cruiser all the front gear box breathers are already mounted high. However, the rear differential and e-locker breathers need to be relocated. For my relocation I used about 4′ of 1/4″ fuel line, a small fuel filter, a vacuum line t, a fitting for the differential and a number of  clamps.

Breather Cap Installed

I used the original breather cap as the cap to my breather extension. I placed the breather up by the fuel fill. The T connector is used to connect the e-locker breather to the relocation line.

T Connector Installed

The installation took an hour and cost about $17.00.

Installed tubing ready to be located with Fuel Fill



Tomas has lived in Colorado since age 5. Having grown up on the Western Slope of Colorado lots of time was spent in the Desert Southwest. Tomas' father introduced him to the love of 4 wheeling at an early age in the high mountains around Aspen, Colorado. While an avid Mountain Biker, Tomas and his Family enjoy adventures in the mountains and desert in the remote locations that can only be reached by 4wd. Day hikes are always a must when on the family trips. While enjoying outdoor activities he wants to share his love as a certified 4wd trainer and ski instructor. Tomas also enjoys caving and cave exploration. Tomas currently resides in Colorado Springs. 

  4 comments for “Rear Differential Breather Relocation

  1. Rocky
    November 23, 2012 at 7:45 AM

    Hi! Great work by the way and congrats; LOVE your FJ. My question is why do you need to install a small fuel filter inline with the diff breather hose? Thank you

    • December 5, 2012 at 4:22 PM

      I use it to trap moisture and dust.

      • Bill
        May 10, 2013 at 3:57 PM

        Hi. Nice work on the mod. I did want to point out something you might want to consider. The stock “jiggly cap” breather that you reused on your tubing is essentially a “one-way” relief valve designed to allow pressurized air to escape, but is designed to close with negative pressure (if you break one open you’ll see a spring-loaded seal that stays in the closed position unless pressurized air forces it open when venting, but closes immediately with either zero or negative pressure). This means that, even with it mounted high, as you rapidly cool the diff while fording a stream, the valve will close resulting in a negative pressure (i.e., vacuum) in the axle tube. This is because the axle tube will immediately want to draw air in to equalize the pressure, but with that valve in place, no air can enter your tube forcing water to be drawn in through the axle seals as the axle housing seeks to equalize (nature does not like a vacuum). The solution is to replace the “jiggly cap” version with Toyota P/N 90930-03136. This is a two-way breather and will allow you to experience the full benefit of your relocated breather.

  2. kevin
    December 4, 2013 at 11:56 AM


    I am planning relocating the vent for the rear axle, but what and where is e-locker

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