Does the Mazda BT-50 need diff breathers?


G’day people!

I this post I want to give people the information on the factory location of the diff breathers so that people can see whether it is worth the hassle of installing diff breathers.

I went through this process of tracing all the breather lines as part of an install I was doing for my 4WD build.

Once all was said and done though I had to ask the question…

Does the Mazda BT-50 need diff breathers? For most people I would say no it does not.

This post is in reference to the Mazda BT-50 from the time it shared its chassis with the Ford Ranger and this post therefore also covers whether the Ford Ranger really needs diff breathers.

Besides the diff breathers, there is also the transmission breather and the transfer case breather to worry about.

I did fit a quad diff breather kit from BRC (eBay), which I will explain the reasoning behind at the end of the post.

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Mazda BT-50 / Ford Ranger Diff Breather Install Video


See the below video for reference where I go through and trace out the breather lines and ponder, does the Mazda BT-50 need diff breathers?


Differential Breathers Basics


Before we I show you why I think the Mazda BT-50 probably doesn’t need diff breathers in most applications, I will very briefly touch on what diff breathers actually are.

What are diff breathers?


Breathers are hoses that run from your diffs (differentials) up to a higher location than the diffs sit themselves so that when they need to take in air, they can take in clean air.

They are basically like a snorkel for your diffs.

As you drive around the differentials get warm and the warm air from inside is expelled through the breather, but when it cools down rapidly like when you do a water crossing, the diff will suck in air quickly.

If your diff breathers are down low, then it could be underwater and your diff will then suck in that water instead of air as it cools down in a hurry.

This will introduce water to your diff, which is full of diff oil, water is very bad for oils as it stops them lubricating and it will ruin your diff if you don’t replace it with fresh oil as soon as possible.



What other breathers are there?


Besides your front and rear differentials, there are a few other things that sometimes have breathers:

  • Transmission.
  • Transfer case.
  • Winches (not always required).
  • Compressors.

Just to name a few, but we are only focussing on the front diff, the rear diff, the transfer case and the transmission in this post.

For the purpose of this post the term “diff breathers” is also referring to those in the transmission and the transfer case to keep the text simple.



Can the problem be avoided?


Yes it can, partially.

Before doing any water crossing it is best to stop, turn the car off and let the components cool down as much as possible before making the crossing.

This is not always completely practical but should be adhered to as good practice as much as possible.

Even with diff breathers installed this is the best thing to do so that the diff breathers work as effectively as possible.

If you are returning from, or about to embark on a lap of Australia or a massive trip through the Kimberley or Cape York for example, just change out the oil it really is a simple job. I use the following oils (affiliate links):

These oils work for me, there are other compatible oils as well.

Diff Breathers in the Mazda BT-50 / Ford Ranger


So does the Mazda BT-50 need diff breathers? Does the Ford Ranger need diff breathers?

This is a case by case basis but I will show you where the factory diff breathers are and let you decide whether the Mazda BT-50 needs diff breathers or not.

I will argue that the majority of people do not need to install after market diff breathers.

The reason for this is because the factory diff breathers are located quite high in these vehicles, this doesn’t apply to other vehicles as each one needs to be taken on its merit.

Rear differential breather


To start with we will be looking at the rear diff, this diff is the lowest of all of the diffs from factory, it comes up with the fuel filler neck and ends just below the fuel filler.



Above is the location of the diff breather should you want to change it out, this photo is taken with the tray removed so don’t expect to have this sort of access.

Beneath is a photo of where the breather runs to.



As you can see the diff breather for the rear runs up to somewhere between 600-800 off the ground depending on the vehicle. It’s reasonably high and higher than most people will ever dunk their car into water.

Does the rear diff breather need to be raised?


I would say that if you were to do any, this would be the one to do.

But the point I am trying to make is that for most people, even this is high enough and would be of little concern when doing any reasonable water crossing.

If you’re going through massive rivers and mud holes you will obviously need to raise the height.

Front differential breather


The next most common diff breather that people will redo is the front diff breather.

This is where I begin to think it is entirely unnecessary. As part of installing my diff breathers I physically traced all of the diff breathers from their locations to the end of the breather lines (with the exception of the transmission which we’ll get to shortly).

Here is what I found.



Number 1 in the photo above is the front diff breather location with the engine removed. Easy enough to access if required from underneath the car.

But below is the location that this breather runs to. These 3 hooked pipe fittings can be found in the engine bay near the fuel filter. They are one of the highest things in the engine bay, sitting up at the same height as your alternator.



I was able to physically trace two of these lines all the way to their source to determine exactly what they are used for. They went to the front diff and the other to the transmission case.

Due to their height I decided not to install a front diff breather despite mounting all of the hardware for the rear breather, it just wasn’t going to give me much benefit.

Does the front diff breather need to be raised?


I think even for those who intend to go into some pretty deep crossings that you would easily get away with not raising this diff breather.

Even where I mounted my diff breather kit (eBay) in the engine bay it would only gain at most 50mm in height. There aren’t many things in the engine bay that sit higher than these three breathers.

Transfer case breather


Transfer cases also have breathers and in this instance it runs very high up in the engine bay as described above I traced this breather out all of the way from start to finish.



Number 3 in the photo above shows you the locatin of the transfer case breather hose.


The issue with the transfer case breather


Although we know where the transfer case breather is, when it is mounted in the car you’ll be lucky to get your hands on it. I could not actually see the connection point, I could only reach my arm up there an grab a hold of it.

There is almost no access in there, but I wanted to make sure that it was at least connected firmly and attempt to push it on further if I could (I couldn’t as it was on firm already).

The issue is that if you wanted to remove the transfer case breather and screw in a new adaptor that comes in a diff breather kit you would struggle to do this given the space and lack of sight. I am unsure if this fitting can actually even be screwed out at all or if it is moulded in.

If anyone knows please leave a comment.

Does the transfer case breather need to be raised?


Given the poor access and the height it runs to in the engine bay I would not bother with this.

I definitely recommend reaching your arm up and ensuring that the hose is firmly connected though otherwise you definitely need to sort something out.

Due to the location of the transfer case breather, sitting up inside a cavity of sorts, there are arguments that water does not fill this spaces in a lot of instances due to air pockets forming.

That theory is logical but I have no way of knowing how it plays out in reality.

Transmission breather


This breather was the only breather that I could not fully trace out to the point it connects to the transmission. Using a workshop manual I found out that the third hooked fitting in the engine bay is for the transmission.

I can see it run all the way to the firewall and to the top of the transmission, but from beneath I can not feel the connection point. 


There is no way to reach it from the bottom of the car, although I do not want to necessarily rerun the breather hose it would be nice to be able to ensure it is secure.

I don’t think it travels much further than the point shown above where I lose contact with it, it can possibly be reached from the top down by removing all of the centre console but I have not confirmed this yet.

Does the transmission breather need to be raised?


I don’t think it does as I am 95% sure that it runs to the third hooked fitting in the engine bay.

If anyone knows how to access the transmission breather (this is an automatic by the way), then please comment below about its location or share any images.

Diff breathers summary


Hopefully that has been of some help to people who those who were wondering, does the Mazda BT-50 need diff breathers?

I think you’re heavily protected in these cars from factory with the read diff breather being the lowest of the three. The majority of people don’t need to install any diff breathers, those that do only need to install the rear diff in most cases.

So why did you install diff breathers?


Why did I install them? I got given the kit from a family member who had sold their 4WD so I thought it was worth the hassle. Finding out where the diff breathers went was part of the install process as well.

Without looking at the install I probably would have gone and bought a kit to install because everyone just assumes you need them, but in reality with this specific car you have a lot of protection from factory.

This post just aims to clear that up for others who are unsure, it really depends on the use case of the 4WD.

The other reason was that I wanted to have the rear diff breather to at least match the other 3 breathers for height. With the hardware installed (the breather quad port) it would be easy to change my mind later and add the other breathers to the port.

Reasons not to install diff breathers


The reasons not to install them is quite short but it would apply to most people.

You don’t do water crossings and the whole thing is a moot point (a lot of 4WD owners).

You won’t be doing extreme water crossings over 800mm (the factory wading depth) and therefore the height of the existing breathers is more than you’ll ever need.

After you consider those first two points you realise that it is a waste of your time and money to go through this install just because everyone tells you you need them. You probably don’t need to do everything the 4WD shop tells you to do. 

Reasons to install diff breathers anyway?


This section applies to the general driver, not the extreme expedition driver who obviously needs them and wouldn’t be reading this post anyway.

These are reasons that you might want to install them despite knowing deep down you probably don’t need them.

They’re a relatively cheap modification to do, often it will cost you nothing more than $100-$200 and a few hours on the weekend.

You’re worried about the factory breathers getting clogged. I don’t think this is a common issue given the height of them on this model of car, but granted the aftermarket filters run through a filter fitting.

If your factory breathers have a 1-way valve then get rid of them, because it will only allow hot air to escape, then close as the diff tries to breathe when dunked in water, meaning the chances of water ingress through the housing seals increases.

Transmission and transfer case breathers


To do these two breathers, if you would rather port everything through the filtered breather housing that you have purchased you might have to intersect the hoses instead of screwing in a new adaptor.

The access is poor and you can always cut into the existing line, push your line inside that line and secure it, then run the new section of breather hose up to the breather port that you have installed.

Does the Mazda BT-50 need diff breathers: Summary


At the end of the day it’s up to you whether you install diff breathers or not, but don’t be bullied into doing it without having a think about your application.

You can still have problems with after market diff breathers if you do a lot of water crossings, so make sure to keep checking diff oil after you have done a lot of crossings to ensure they’re still operating well enough.

If you know any more about whether the transmission and transfer case breather ports are moulded or screw in please let me know, as well as how you might access them to do a full replacement job.



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