Minute Mod: Differential Breather
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Author: Scott Wilson March, 2000

A differential breather is a vent to the outside air, covered by a cap that helps keep debris out. This breather is usually in the top of the axle housing, above the differential. The breather is necessary to relieve pressure in the axle housing caused by temperature changes. Without a breather, or if your breather is clogged, the pressure that builds up inside the axle housing will most likely push gear oil past your pinion or axle seals.

Since the breathers are located right on the axle housing, it is possible that they could be submerged if you were crossing a creek, deep puddle, or mud hole. The potential for a problem arises when you submerge the axle for more than a few seconds. The temperature inside the axle drops which causes the pressure inside the axle to also drop. This pulls whatever is on the other end of your differential breather into the axle housing. If you're axle is under water, it will be pulling in water. If you've pulled in water, you need to chage the gear oil soon, or down the road you'll most likely be looking at some damage.

By raising the point at which the breather draws in air you can significantly reduce the possibility of getting water in your axle. This is commonly called an 'extended breather.' One easy method of creating extended breathers is to attach a vacuum hose or fuel line to the breather, and route the other end of the hose to a high location in the vehicle. On my vehicle I have routed my breathers to the top of my engine compartment.

Inexpensive breather fitting

The stock Toyota differential breather leaves very little room to attach a hose once the breather cap is pulled off. There are a couple of other fittings that can be used to replace the stock differential breather, each with a long stem that you could easily secure a hose to. There is a fitting on the Toyota 4 cylinder intake manifold that will serve this purpose well, but if you have to buy the fitting new, there is a cheaper alternative.

There is a Nissan breather that fits perfectly into the threads that our stock Toyota breathers use (except Land Cruisers). The Nissan part number is 38323-C6010. I was charged $4.50/each for the breathers I purchased. The picture on the left is what the nissan part looks like sitting in the top of the Toyota differential housing.

Rubber hose breather line

To extend my breathers I used is 7/32" vacuum hose, available at most auto parts stores. To make sure the hose does not ever come off of the breather fitting I also clamped it down with a very small hose clamp. These should also be available at most auto parts stores. Here is a picture of the finished product.

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