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Saturday, November 27, 2021
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Why You Need Diff Breathers

photo by Luka Banda via iStock

A huge wave comes raging over your windscreen, your engine screaming, and your seat getting dirtier and dirtier – congrats, you’ve just tackled a deep river crossing. 

Water crossings can be one of the most thrilling experiences one can have in a 4WD (when they go well). However, as you can imagine, vehicles do require preparation to tackle such challenges. 

Some of the mods like a snorkel are obvious, but there is one very important upgrade that often gets overlooked.

That item is the diff breather, and today we will be covering everything you need to know about them. 

What are Diff Breathers and Why Do You Need Them?

Diff Breathers

All 4x4s have diff breathers from the factory. They are usually located on the differential or slightly higher under the floor of the vehicle. 

The diff breather is a one-way valve that enables air to escape from the diff when it warms up. In most cases, air cannot go back in through that same valve. 

The reason they exist is to equalize the pressure within the differential due to temperature differences. 

However, they do not work as well when it comes to river crossings.

For example, let’s say you have been driving on the motorway for a couple of hours, you then exit and enter the trail. As soon as you enter, there is a river crossing that you know is deeper than the height of your axles. 

Since you have a snorkel, you go for it and everything seems fine, but it isn’t. That hot differential has now been dipped into cold water; therefore, its internal temperature has dropped quickly. 

Truck in the River

photo by dangdumrong via iStock

That difference in temperature means that the diff is trying to contract and while it does it creates a vacuum that will suck air back inside the diff. Since the breather is a one-way valve the next weak point is the seals on the axles. 

However, the axles are submerged in water which means that instead of sucking air it will suck water. The water then contaminates the differential oil, and it all leads to a very expensive repair. 

How Can We Prevent This?

Extended Diff Breathers

The above problem may sound serious, but adding diff breathers is one of the simplest and cheapest modifications one can do to their truck. 

The procedure is simple. You start by removing the old one-way diff breather that is mounted down low, and you replace it with a long piece of hose that goes to the engine bay or even higher (if possible). 

That piece of hose is then connected to an aftermarket breather that enables air to escape, but also to be drawn back in. 

Because the breather is now a two-way valve, air will be able to get sucked in through there instead of the seals. Furthermore, it is now mounted up high; therefore, there is no fear of water ingress from there. 

Who Needs Extended Diff Breathers?

Extended Diff Breathers

photo by istock80 via iStock

As you can tell, diff breathers are only there to serve the purpose of driving through deep water. 

If you live in a part of the world where deep water crossings are non-existent or even if they are existent, and you tend to avoid them, then diff breathers are not necessary. 

However, if you often find yourself in deep water, then the above modification can save you thousands of dollars. 

Keep in mind that breathers can also be added to transmissions and transfer boxes, and they serve the exact same purpose. So, just bear these tips in mind and you could save yourself a lot of headaches!

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