Rear differential breather question.
 

This weekend I was changing motor oil on my 96 4Runner (4x4, auto). And I deicide to take look at differential oil level. When I pull the plug from rear differential I heard the hissing sound of air and that scared me. So I immediately thought that breather is clogged up, but after I pulled the breather off I was able to blow the air through it with no problem, but I was NOT able to suck the air back in (it has a cup that just sits on the top but id does not effect the functionality of this thing). So the hissing air sound I heard was air going in to the differential because of the vacuum that was created there.
I also checked front breather (it on the robber hose, under the hood) and it lets air in and out. So I called local Toyota dealership and explain to them my concern and they told me that my rear breather working properly. What you guys think? Am I missing something?

i dont know, but i am going to be checking my rear diff fluid today if i have time. if not today i will probably do it before this weekend. ill try and let you know what happens with my truck.

doesn't seem like there should be a vacuum in there. but i dont really know, maybe somebody else will know for sure.:dunno:

if the dealer says it is supposed be like that, it probably is... right???:P

Uh that's weird. Take your rear diff fill plug out and check the level ignor the hiss. The breather is suppose to be one way so blowing into it is pointless. When you remove the diff plug look to see if there is flothy white stuff in it(might cause the hiss) If so drain ASAP cause this is water.:)

while putting in my lift kit this weekend i happened to check out my diff breathers also , i lifted up on the cap and got a rush of air . mine might be not working properly though . i plan on putting extensions on soon with a filter , so im not to worried.

airrikk17

If you look at Bob's write-up he cautions everyone to expect a hissing sound when pulling the plug for the extended diff. breather mod.

Relax, it's normal.:D

Is it better to use a breather from Toyota or a fuel filter? Or does it really matter? :dunno:

Guys,

I used all Toyota parts. http://www.4runners.org/articles/typerdiff

The hiss scared me so much that I hit my head. Yup, its normal. :nerd:

Bob

I think the fuel filter is better. If the vacuum is great enough when you dunk the axle under water you can suck water into the housing from the seals.

So using a feul filter will allow for equal air pressure for outside air and inside the diff...... Surely this is better than a one way breather valve then or am I missing something?

And is the fuel cap area the best place to route it to?

There was a discussion on this last week. Most everyone said that the fuel cap is just a convenient place because it's a visual landmark so you know where it is instead of having to guesstimate if you put it elsewhere.

Personal preference it seems :dunno:

got the same thing on my 02 its normal.

The stock breather cap is not air tight in *either* direction. It is designed to *burp* outward more easily than inward so that it will resist water pouring in, but it is neither air nor water tight in the incoming direction.

The idea is that when you hop in and start using your rig, the diff goes from the ambient temperature to pretty damn hot in a big hurry. It needs to get rid of some pressure to maintain your seals, so the breather burps it out. When you park the rig for the night, it cools down slowly and air slowly equalizes the pressure, until the next morning when you do it all again. You could run with an open breather without effect on the function of the diff, but for obvious reasons, we don't. Some breath in slower than others, so if the rig has been recently driven before you do the mod, you might experience hissing as you remove the cap from the stock location as air rushes into the vacuum. But rest assured, if you let it sit long enough, it will eventually equalize.

Personally, I prefer to use the stock breather cap when I extend the breather. It offers some level of protection again water ingestion on those days when even extended, it is not high enough.

Thanks for the explanation Rob! :bigok:

Helps a lot more than the "it's normal" reason :hillbill:

Re: Rear differential breather question.
 

My thoughts exactly! I just completed my rear diff breather extension yesterday, and I also heard the same vacuum hiss when I removed the original breather. I thought, "Bob_95SR5's write-up mentioned the hissing, but is the old breather clogged...". WATRD's explaination certainly seems reasonable, but shouldn't the pressures COMPLETELY equalized at some point?? My rig hadn't moved for over 16+ hours by the time I started the rear breather extension.

Re: Re: Rear differential breather question.
 

First of all thank you everyone for response.
And as far as stock breather ..I think it has only one way valve on it which does not make any sense but that is way all people keep hearing hissing sounds, when they do mod.
(unless Toyota knew about rear end seals problem and made it with purpose, so the vacuum will suck all oil back in the rear end, after seal will go.. ha-ha-ha).
Thank you all again.

Ok all I have just the thing for everyone.

This is from a friend:
http://www.wattora.com/Mods/diffbreather/

Just so you know I have my rear breather extended into my gas fill compartment, and the front breather is extended to the top of the engine compartment with a gas filter at the end.
-Mike

hehehhe Now THAT looks familiar... ;)

LOL Ya and you got mail:bounce:

For those of you with 2nd gens that extended your breathers,

Does that union fitting listed work even though it is for the 3rd gen? Did you run into any problems extending the front diff or transfer case with these parts?

I'm trying to figure out the best way to extend my breathers.

Thanks

:bounce:

As for the rear breather union fitting, I believe it would work. I would get the union and see if it fits, if it does not then I guess we need to find the size for your diff.
The front diff breather now theres a story.....

I have an ARB front locker, and one day I noticed some oil dripping from the fitting on the diff from the air compressor line. So I reached up there with my fingers and it was loose; what does a typical gear head like me do? tightens it. Well, I took it out and played in the dirt for a bit and noticed more oil, confused and getting pO'd, I drive back to home base and take the fitting out.
There, I fixed it with High Temp Thread Lock! Went back out and played in the dirt, locked my diff in front and PRESTO....I got gear oil puking out my breather and my ABR Compressor relief.

Oh Sht, did something bad but don't know what; so I took my truck back to 4 x Doctor where I had it installed. Turns out..... now if anyone has a Tacoma better listen......that the diff has very thin walls, the ARB fitting was too big (ARB at Fault) and it did not grab the threads, Mike Duncan and his Mechanic "Jim", took out the diff and looked into the ARB fittiing, they came to the conclusion that ARB had the wrong fitting for Tacoma and Mike had to JB Weld the hole made for the fitting and redrill a new one closer to the Mold of the diff so the threads would grab. They used a tapered Tap so the threads would get tighter as they installed the fitting. The end result that caused the puking of gear oil was the ARB copper tube in the diff, it was too close to the Gear bolts, because the fitting, when tight, would push the copper tube close to the nuts on the gear, thus rubbing on the tube and eventually got a hair line hole in the tube to pass air into the diff.

So, if you wonder why I am using a fuel filter instead of the breather, LOL I blew it off the hose from the diff and could not find it.
-Mike

Happy reading :yawn: