Hi guys,

First off all, let me express my deep esteem to this awesome site and people posting here and sharing invaluable information from their experience.

Second, I hate any mods on any cars unless they are legit.

Have said that, here are my few challenging questions about the rear diff breather, you all recommend to extend to the location where water no longer can reach (with common sense in mind of course). Alright here you go:

1) Literally all off you reported a vacuum hissing sound while removing the factory installed breather on the rear diff. Some of you noticed this to happen after as long as 16 (!) hours of not driving! There is no need to be an engineer (I am am engineer BTW) to conclude that the factory breather is the one way valve. As such, and since even air cannot get in, in my mind there are NO CHANCES that water can get in either,

2) From my working experience, any tubing, attached to a relief valve which normally expels oil fumes (diff breather does that, right?), are prone to easy clogging due to long way to get out. Basically, oil in relieved air will condense along the way on cold walls of the tubing causing a quick clogging of the breather system. Consequences of that are known, and they are bad,

3) Have any of you experienced leaking diff seal with a breather extender installed? Or vise versa, have any of you without breather extender experienced a water contamination of diff after a river crossing?

4) Why in your opinion Toyota neglected this thing if it is really so obvious problem?

Thanks in advance to everyone responded,

I think this thread would be more appropriate in the General Discussion or Off-Roading forums as this is not specific to 5th Gen only.

1) A very good point, I was pondering the same thing. The reason I installed the breather extension is to PREVENT a "catastrophic failure" of the breather getting stuck in an open position (see your point #2). May not be much of a concern for folks with trucks still under warranty, but I'm past even the drivetrain warranty. BTW, there was no hissing sound when I removed the breather, but I tested it and it did hold vacuum.

2) That's a statement, not a question... I used a fuel line for that mod, and I'm not sure how much the oil condensation may be a problem in the line. Not only the oil has to form a condensate droplet on the wall of the line, but it would have to aggregate to a significant degree to clog the line. I'm not an engineer, but have had experience working with all sorts of tubing and fluids. May be someone with a chemical engineering background or a wizard-mechanics can chime in on this.

3) I had a leaking seal BEFORE the extension... It has been 2 weeks since the seal replacement and breather extension, so I'll be in the shop next week to check things out.

4) I know it's not polite, but I'll answer your question with a question - Why would Toyota extend breathers on transmission, front end, and transfer case?

[QUOTE=snhrph;619606]I think this thread would be more appropriate in the General Discussion or Off-Roading forums as this is not specific to 5th Gen only. QUOTE]

I was thinking about that too. But since I have 5gen 4R, and it is my first 4R to begin with, I thought: well, I know nothing about previous generations, so the problem could be easily related to them only, and 5gen has solved that issue at factory all together. Sounds like it is not.
Anyway, I would not mind to move the tread, but do not know, how.

Just crawled back from the underneath of the truck. Two observations.

1) The factory installed breather is still higher than a lower edge of doors. I think I would be much more upset because of water pouring into the cabin, than few drops in a diff. It is unlikely I will go that deep

2) I noticed a number of electrical connections such as the fuel pump control box and trailer connector to name at least, hanging as low as the original breather. And it seems to me no one really worries about a short in them due to a water submersion. This would pose a much bigger treat to the vehicle than a wet differential.

Does it make sense?

The breather mod is just a precaution for people who regularly ford water. Obviously, the check valve "should" work as is, without sucking water into the diff. However, having one stuck open will result in more than "a few drops in the diff". Having it vented to a higher point will prevent any problems for people who expect to dunk their rear diff in water as they travel.

And while a wet wire short might cause you to stall in the middle of nowhere, a frothy differential will absolutely burn itself up. I can wait for wiring to dry out (or use WD-40) but I don't carry spare differentials with me.

It's a simple mod that costs a few dollars and takes minutes to do. Peace of mind makes it worth it.

I bought a 91 toyota 4x4 brand new and had a burnt outt diff at 1000K . Launching a boat trailer , I must of went over the breather and it filled my diff with water, didn't check it untill I could hear a slight hum from the rear end while coasting . I opened the fill plug to see if it was low on oil or somethig from the factory (yes I,ve seen this before , I now check all fulid levels on all new to me vehicles as soon as I get them) and milky water/oil shot out 5 feet when I removed the plug. I immeditaly did the mod after this mishap and this was back in 91 . The factory breather is no good , I wouldn't trust it anyway ,all it takes is to get a little mud in it or even dust with a little water mixed in and that alone will bind up and render the little flimisy spring in there useless and leave the seal open or it could seal shut and blow out you pinion or axle seals. Get rid of them , I use a cheap fuel filter on the end of my extended hoses for many years without issue..

found this thread (pretty old one):New 4Runner water fording height?

The quote from Guest:
"The breather is a loose one-way valve. If the pressure sucks in, it closes the breather. If the heat builds up, it blows out.

Is there a chance debris could block open the breather? Yes. Is it probable? No. The breather is on top of the pumpkin where there is no debris flying from tires or body and blocked by the frame cross members and underbody.
Could a rock jam it open? No. The way the breather is made the gap has a lip that makes the gap so small, the only possible thing to jam it open is debris like mud if you sunk in up to the axles.

Driving through water, the bow wave is created where most of the water is pushed by the front of the car.

If you want cheap insurance, extend the rear breather. It takes 10 minutes.
But through experience, I have found it not necessary. If I were fording deep water on a regular basis, I would extend to be on the safe side but the rear diff is well protected as is."

I should be really damn crazy to get stuck in a such deep mud to get valve jam open. So, no such mod for me.

Do some reading as their are more than just a few stories of water logged diffs and since the mod is so cheap it's better to eliminate the chance than take it.

It's not the water coming in the breather,it's the water coming in the differential seals. The breather can't vent it when it's under water.There are plenty of expensive horror stories of this happening!

It literally takes about $10 and 10 minutes of your time to help insure against thousands of dollars of repairs.Now that's cheap insurance!Dozens of DUI write-ups on it.Even an engineer could probably do it! JK
What type of engineer are you BTW??

Differential breather relocation

Toyota 4Runner and Pickup: Waterproofing Tricks

The question is ...why do manufacturers take the time and money to raise the tranny,transfer case and the front breathers but not the back?????????It's the cheapest and easiest one to raise!

If the water coming thru the diff seal, relocation the breather doesn't seem to take care the problem. IMO if the the breather is the oneway valve i believe the water can't get in thru the vale unless otherwise the temperature in side the diff is lower than the out side, as long as the temperature inside is higher than the outside the pressure will expand outward therefore no water could get in.

Hi all!

Some personal experience with the breather... Living in the North East, recently found mine to be corroded to the point nothing got past it. I replaced the breather, hopefully it was in time to save axle end seals from getting pushed out from pressure increase in the housing. Fingers crossed~

Toyotee

Hopefully you relocated it to the "higher ground".

Chemical engineer.

I believe due to the rapid cooling of the diff when it's submerged under water the diff will create a suction effect, if the diff breather valve is above water, your OK because the diff will suck air through the breather valve. If the breather valve is under the water, the pressure from the water will close the breather valve, therefore the diff will suck air in via the diff seals. The breather valve is just a cap with a spring in it. Normally air can be inhaled and exhaled, unless the cap is closed due to "water pressure."

Hope that makes sense, that's how I summed up years of reading about this diff breather mod and whats the purpose. I performed this on my 1988 4Runner, my 2000 Cherokee already had the breather relocated, and on my 2008 Tacoma. I am gonna perform this mod on my current 4Runner within the next couple weeks.

Sorry to resurrect this old thread / argument, but I just did the diff breather relocation this weekend and had a question...

So I bought the replacement plastic plug breather vs the factory metal threaded and actually decided to use the factory one at the end of the hose. The breather seemed to work a lot better as the plastic one seemed to get hung up on itself.

Since I am new to this mod, I thought I'd bring this up for those who have done it frequently in the past and had it on their rig for several years. I don't want to decrease the life of my axle seals and I've read that with newer vehicles it is often better to have a fuel filter or other type of free flow filter at the end of the bypass hose instead of a breather plug.

I believe the argument is that it allows equal pressure at all times so there is no chance of pressure build up / seal destroying. What do the smart guys on this forum think?

I did my diff breather mod last week. The breather that I put in at the end of the hose isn't like the factory one. It's cap doesn't move, it allows air to be exhaled and inhaled, whereas the factory one only allowed air to be exhaled I think. I do remember when I unscrewed the stock breather, I heard a whoosh of air.

I routed mine up to the fuel filler hose. I just zip tied it and the actual breather is now higher than the fuel door inside the fender.

I'm with you, I think the diff as a whole would benefit from a free flowing breather, however at it's stock location, it would constantly suck up water going through puddles and etc. I would think.