My Differential Breather Mod Photos

Thanks a lot, CowboyTaco, DoorDing, and David K, for your helpful responses!

I did say underbody instead of truck bed because this is indeed a 4Runner. The breather is tied to highest point of the underbody directly above the rear diff.

I am concerned about dirt, grime and salt because this is not as protected an area as the engine bay where the front diff breathers are. Besides, this is not even above tire height, which I believe roughly equals wading depth (about 70 cm).

Therefore, I am planning to follow the instructions in the posts cited above and relocate this breather to the tail light cubby. That seems to be a great place for it.

Thanks again!

 

Sounds like a good plan laufer!

 

Sub'd

 

Subd

 

OK, been getting a few messages and replies here from folks needing details that were in the first post... so please read my first post, re-posted here so you don't need to go all the way back to page 1.

 

Maybe replacing that yellow tube with pink or something. Easier tutorial that way lol

Had to get my truck align 3 times this month. Every tech asked me what that orange tube for. Easy mod and some day save big time.

 

subd

 

Finally got the motivation to do this, and ordered parts from this site. Love the $3 shipping cost. Thanks for the link.

And thanks, David, for re-posting on this page. I plan to route to the tail light, though.

 

Is the factory breather a one way breather and only lets fumes out? If so, why do we need to do this?

 

Factory vent has a check valve to only allow venting out. If a hot diff gets submerged in say a cold stream, there can be negative vacuum, and the factory vent will not allow air back in. Water could get sucked into the diff through the axle seals. It's happened to some.

From a 4Runner forum:

The rear axle, instead, has a little breather cap (withOUT the hose) on top of the axle. The silver cap acts as a one-way valve. When the axle housing gets hot and pressure builds up, the cap pops open, releasing the gas and then closes down to prevent water from getting in. HOWEVER, in theory, this cap can malfunction, especially when you have mud/dirt sticking to it. This can happen if you off-road often or cross streams often. And if it malfunctions, then water/mud can get into the differential housing. That would be bad.

 

It is fully explained on page 1 when I made this thread...

If, after reading my explanation there, you need other details, I am happy to try and help.

 

Thanks. Makes sense now.

 

Now? On the first page, in 2010:

"The new breather fits perfectly inside the 3/8" I.D. tube. Unlike the original breather, the new one does NOT have a check valve (a one way valve that lets gear fumes out, but nothing in)... That was reported already, so I was not surprised. I guess my diff. was contaminated by muddy water getting in through the axle seals...?

Having a two-way breather would act as a vacuum breaker and allow clean air to return to the differential during a negative pressure occurance (like dipping a hot differential pumpkin into a cold stream)!"

 

You know well that many never visit post 1, page 1, or any of page 1, for that matter.

I, on the other hand, could use the part of my life back spent reading through every page of some long-winded threads (not this one - I wanted to see every post)...

I was just responding to cstallings' query yesterday since he apparently didn't look too closely at page 1.

 

I read that post, but didn't correlate the negative vacuum sucking water through the axel seals. I thought you were saying it seaped in or you had a bad axel seal.

 

No problem, I was just wondering how it was missed... that is the reason for the mod. My truck was new (6 months old) when it was in 2-3 ft. deep muddy water. When serviced after the trip, the diff oil was milky (water contamination). I did the mod, and 5 years later still no contamination.

If the front differential has a real (2 way) breather, then why wouldn't the back one get it from the factory too??? Well, it has it now!!!

 

I was concentrating on the breather to much so when you said axel seals it didn't strike me as a place of suction, but I understand how it can be. I was thinking to hard...ha ha. Similar thing happened to my truck that happened to yours when it was brand new, so I wanted to make sure I understood it and not just followed a thread. Thanks for the post

 

hey just wanted to say I just did this mod today, first mod to my truck, and it went super smooth and easy because of this tutorial! thanks a bunch, much appreciated

 

Glad it helped ... wheel freely now!

 

Just thought I would add the fact that I changed the rear diff fluid recently at 40k mi and it looked good just worn out. I did the mod when my truck had about 6k mi on it. I went through many water crossings since I've owned the truck. Kudos David