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2004 4Runner Rear Diff Breather extension by Expat

This is a pretty straightforward mod and gives a bit more insurance to oil contamination in deep water/mud crossings. Only difference from others is that I retained the stock breather instead of replacing it with a new one. The one I bought new from the dealer had a plastic cap instead of the stock metal one and it didn't pop up freely and didn't have a one way valve in it. The stock one worked fine when I blew through it.

The parts needed for this mod can easily be obtained from your local dealer and auto parts store:

  • Toyota Union Fitting- #90404-51319
  • Toyota Breather Plug- # 90930-03136 (Which I didnít use)
  • Same gas line that fits snug to the union
  • Clamps to secure the gas line to the union and breather
  • A few cable ties to secure the line to the frame and filler neck

Here's the stock breather and the replacement breather (which I didn't use)

Here's the union that replaces the breather in the diff. Simply remove the breather form the diff housing with a wrench and put in the union. You will need to remove the spare tire to allow access to the diff and frame.

Now secure the line to the union and clamp down. You might want to heat the line in warm water to make it slip on easier or put a little oil on the union to make it easier to fit the line.

Carefully route the line next. Try to keep the tube from having a low point for diff oil that blows out, from pooling in tube, and make sure you have enough tube to allow for suspension travel to fullest extent. Below are a few pics of how I routed my line. Secure the line with cable ties to the frame.

Route the line upward to the gas cap. You can move the rubber around the filler neck to allow you to slip the line through it. Cut to length and insert breather cap and secure with clamp. Again use some oil to make it an easier fit for the breather cap if required. Secure the line to the filler neck with some cable ties and you are done. Below are the final pics.