Installing Diff. Breathers

Do you do any water crossing when you hit the trails?
Hate having to change the differential oil after having your fun?
Here's a mod that will let get into deep water and also save your oil.

What IS a differential breather?

Every differential has a breather. It is usually just a vent to the outside air, covered by a cap that helps keep debris out. It is there to equalize the pressure in the axle as the temperature within the axle 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.

Why would you want to modify the breather?

The stock breathers have no way of keeping water out of your differential case if you submerge the axle. (i.e. stream or river crossing, etc.) The problem is, when you submerge the axle (for more than a few seconds) the temperature inside the axle goes down and the pressure inside the axle also goes down. This pulls whatever is on the other end of your diff. breather into the axle housing. If you're axle is under water, it will be pulling in that water. If that happens then you'll need to change the gear oil soon, or down the road. And there's the chance you might be looking at some damage and quite a few pretty pennies will be needed for the repairs.

What is the objective of this mod?

The idea is to get the breather to draw in air from the highest point possible. To do this you can extended your breathers by running a hose up into the engine compartment, or other convenient high location.

  1. Toyota fitting - Part No. 90404-51319 - $7.00 (Thanks Hoodlum for the Part Number and price)
    Nissan fitting - Part No. 38323-C6010 - $4.50 (Thanks Erik for the Part Number and price)
    NOTE: The fittings are off of the intake manifold. The only difference is that the Toyota fitting is longer and will give you more area to attach a hose to. Either one will work great.
  2. 7/32" Vacuum Hose (length will depend on where you decide to run it)
  3. 2-4 Hose Clamps
  4. Filters (optional)
  5. Small Springs (optional)

breather fitting Remove the stock breather and replace it with the Toyota or Nissan fitting. The difference between this fitting and the stock Toyota breather is that instead of having a cap to keep debris out, it just has a long stem, perfect for attaching a hose to. The picture here shows what the fitting looks like attached to the top of the axle housing.

Some people have just ripped the cap off the stock breather and attched the hose straight to it. This will work too, but the only problenm is that it doesn't give the hose much to hold on to, especially if you happen to catch it on something (i.e. branch) while on the trail.

breather hose Here is a picture of the hose attached at the axle. You can see part of the fitting, the hose that is attached to it, and the small hose clamp I used to keep the hose tight on the fitting.
Click image to view larger.

filters front breather Here (pictured left) you can see the yellow fuel filters I did at the end of both breather lines (to helps keep dirt out), in the engine compartment. Any standard type of fuel filter will work for this as long as it fits the size hose you use. The filters are not absolutely necessary, you can also just have the end of the hoses so that they are turning downward. Just make sure not to kink the hose so the diffs can still breath. Another way I did this was to use the stock breather off the axle and stuffed the treaded end of it into the hose. (pictured right)

Here are a few other ways I ran the hoses which made it easier to install and saved on the amount of hose needed to run the rear one to a higher spot.

hose behind tail light As you can see in the pictures here I ran the rear hose up behind the the tail light. At the bottom of the of the light compartment area (upper right) there was a hole between the two body panels. At the top was the same thing, but the hole (lower right) was a little smaller then the outside diameter of the hose so I had to force it through. This worked good for also holding the hose so I didn't have to tie it down to something. I have also done this with the stock breather on the end of the hose also. You'll just need to push the hose through more to get the breather on, then pull the hose back into place. hose bottom hose top
hose behind tail light Here I did the same as the last one above, but stopped it behind the tail light and turned it back downward with the stock breather on it. To hold the hose I zip tied it just below the tail light compartment.
One other way I did this was to use some coiled hose. On the back I made it so that the hose coiled around and zip tied to the shock crossbar. It also has the stock breather clamped to the end of it. This was done on a rig with a flatbed, so there was no place above the bed to extend the hose to. rear hose
front hose For the front the hose is zip tied off in the engine compartment with a K&N oil breather filter clamped to it. I did originally have a K&N filter on the rear one too, but it seemed to get dirty too quick.

Now to finish this job off I took some small springs that I picked up at the hardware store and wrapped one end around the hose and stuck the other end through a small hole I drilled. As you can see for the front hose spring (below left) I drilled the hole into the side of the motor mount. And for the rear hose spring (below right) I drilled the hole into the end of one of the spare tire braces. This will help in keeping the hoses up out of the way of getting caught on debris sticking up from the trail and still let it move around when flexing. With the coiled hose I didn't need the springs cuz the hose did the same thing by itself.

front spring rear spring

These breathers perform at least as well as breathers that sell in magazines for well over $50

NOTE: I've heard from a Land Cruiser owner who says the fittings DO NOT fit in his diffs. If any LC owners have used one of these fittings with success, please contact me and let me know what year and model Cruiser you have.

I've heard back from one Land Cruiser owner who says they DO NOT fit in his diffs. If any LC owners have used this part with success, please contact me and tell me the year and model Cruiser you have.

There is also a Toyota part that will accomplish the same goal as the Nissan part... it will give you a larger area to attach a hose to. The Toyota part is a fitting off of the intake manifold. The Toyota part number is 90404-51319. I do not know what this part costs from Toyota. Thanks Jeff Sturgeon for tracking down the part number.


The information provided above was submitted by a visitor to takes no responsibility for the accuracy of the information above., it's owners, or Toyota Motor Company deny any liability for actions taken based on the information in this article and will not accept responsibility for damage incurred to any vehicle, parts, or person, based on those actions. As always, encourages its visitors to seek the advise of a professional before attempting any modification to any vehicle.

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