"Type R" Extended Rear Differential Breather
By: Bob_98SR5

Toyota Union Fitting- #90404-51319 (~$6.00)
Toyota Breather Plug- # 90930-03136 (~$3.00)
Fuel Hose Line (5 to 6 feet; ID 3/8", OD 1/2")
1/4" - 5/8" Hose Clamp (2)

Tools/Supplies Needed
14mm rachet socket
12mm rachet socket
Flat-bladed screwdriver
Xacto knife
Pipe Thread tape
Large Cable Ties (2)

Obligatory Disclaimer

I am providing this write up for illustrative purposes only. Perform at your own risk. Any mods (including this one) you perform on your vehicle is your responsibility. Furthermore, commercial use of this write up is prohibited---all images and text are property of 4Runners.org. Linking or copying any portion of this write up will result in legal action.

If you plan on or anticipating off-roading in fairly deep water, extending your rear differential will help you prevent damage to it. The stock rear differential breather plug only extends about an inch above the differential itself. When fording deep water, the cool water has a high probability of being sucked into the differential through the stock plug and as you know, "oil and water don't mix." The key to this installation is to basically raise the breather plug higher than what you anticipate driving through.

As with most mods, there's always room for improvement either in the process or the parts used. Thanks to some rather specious sources, I acquired a very "special" differential plug that allowed my differential to breathe easier and amazingly add an additional 50 rear wheel horsepower! Skeptical? Read on! And of note, thanks to Jalaber's excellent write up on his website, which I used as a reference to perform mine.

Step 1: Removing the Spare Tire

You'll need some room down there to work so it's best to remove the spare tire. The spare tire is removed by using the supplied tire tool to lower it from its mount. The tire tool is located under the rear seat. After removing it from its plastic clips, insert it into the hole located in the rear cargo area and turn counter clockwise. You will see the tire lowering.


Lift up the passenger seats and you'll see the tire tool

    Place the tire tool in this hole, make the connection and turn counter clockwise to lower the tire

After it is completely lowered, slip the plate out of the tire, roll the tire in a safe location and then pull the tire wire up.

Step 2: Removing the Rear Differential Breather Plug

As you can see here, the rear differential breather plug is located on the left side of the rear axle.

Rear axle view from the back. The stock plug is shown as (D)   Close up of the stock breather plug

Remove the breather plug with a long 14mm rachet socket. Be forewarned, it will hiss as the gas pressure escapes from it. I got a bit startled and hit my head. Ok, back to the write up: After removing the plug, tape some thread tape on the new union fitting and use a long 12mm rachet socket to fasten it onto the rear differential.

OEM Stock breather plug (O); New "special" breather plug   Thread the new union fitting with thread tape and fasten w/ a 12mm rachet socket

Step 3: Threading the Fuel Line
Here's where I did things a bit differently from others. First, I removed a plug that holds the gas line cover to the body. You really only need remove one single plug (pic below). Wedge some paper in between the body and the gas line cover to allow the fuel line to slip through.

View from underneath: (G) is the gas line cover and (P) is the location of the single plug you need to remove. After removing the plug, wedge some paper to create a gap   This is the plug you need to remove. The plug has two tabs (T) that you must push in to remove the plug. Use a flat bladed screwdriver

Next, use your Xacto knive and cut an "X" shape in your gas filler gasket. I cut mine on the right side, but in retrospect, it might have been better to cut it a little higher and to the left.

Cut an "X" shaped hole in the rubber gasket and feed the tube downwards. If I were to do it again, I'd cut the hole a little higher and to the left   Here's the differential fuel line coming through the gap you created (G). As you can see, the plug (P) is removed

Feed the tube downwards and it should go through the gap. Note: it took me a few tries to successfully thread the tube through so don't give up after the first try. You'll notice that there is enough space for the new fuel line to peacefully co-exist with the existing fuel line. You can now insert the plug back into the gas cover.

Step 4: Connecting the New Fuel Line to the New Union Fitting
Once you've finished threading the fuel line down, run the fuel line as shown across to the right and down to the new union fitting. Leave some slack for suspension articulation. Next, take your Xacto knife and make sure that the fuel line end is cut straight. Fasten the hose clamp onto the end about a 1/4" from the bottom. Moisten the union fitting w/ a little water or saliva, push the fuel line/pipe clamp onto it and then tighten the hose clamp.

Here's the new fuel line (G, marked with yellow) threaded from the gas line cover and running to the new union fitting.   Here's the new fuel line, hose clamped onto the new union fitting

Step 5: Type R Power!
Go back to your gas filler nozzle area and cut the new fuel line tube to length. As you can see, I purchased 6 feet and I have quite a bit left. Now, insert a hose clamp to this end of the fuel line and then (drum roll, please) insert the "special" Type R breather plug. Yes, you heard it first here at 4Runners.org---a Type R breather plug! See the pic below.

Here's the new fuel line. Cut to length. In this pic, I prematurely put on the hose clamp so I wouldn't lose it.   A Toyota first! If it works for the slammed Honda crowd, why shouldn't it work for us?

Now put your spare tire back. After final fitment, I took a little drive. I immediately noticed that at WOT, I was just moving as if someone dropped in an LT1 engine---Good lawd! I can wholeheartedly say that the Type R breather plug is responsible for this massive increase in horsepower!

Questions or feedback? Email me and I'll try to get back to you. If this article helped you save time, money or just made things more convenient for you, please consider donating to keep this site alive.