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Discussion Starter · #1 ·
I have the usual breather extension kit from Marlin Crawler. I was inspecting the breather cap and I noticed that it seems to let air out but it doesn’t to let air in. I was testing it by blowing air in the tube and then sucking air through the tube. Blowing air through it worked but sucking air through it doesn’t work. . . .

I realize that it is more common for the differential to go from a cooler temperature to a hotter temperature when you start driving around. As the air heats up it expands and the pressure is released through the breather. . . . But I was concerned that when a hot differential is quickly cooled down (like when driving through a river crossing), then the air condenses and creates a vacuum. This requires sucking air through the breather. . . .

Am I missing something here about how that thing works? . . . Otherwise, I was thinking that maybe I’m better off replacing the breather cap with something else like some filter cloth that will keep dirt out but let air pass freely both ways. . .
 

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What your thinking is right. What you need to think about is when your diff heats up it is gradually. When it cools and needs air it is a slow process. There isn't any vacuum. It's more neutral. When crossing water it's a raped temp change so it closes. It will open again to neutralize the pressure when equilized.:2cents:
 

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diff

If iar did not get out it would blow yer axle seals and gear oil out on the brakes.
If it needs to take air in it can to a certain point,if it draws air too fast it will close.
 

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Discussion Starter · #4 · (Edited)
When crossing water it's a raped temp change so it closes. It will open again to neutralize the pressure when equilized.:2cents:
Hmmm . . . But I guess that’s precisely my concern . . . From experimenting with the breather valve, it seems that it doesn’t open up again. It’s like a one way valve. Air can get out but I don’t see how it gets in. . . .

So I’m thinking that these valves are actually suited only for street use. On the street, you would only really have an issue with the diff going from a low temp to a relatively higher temp in a short time. (Like if you start your truck and get on the freeway.) But the opposite wouldn’t really happen. When you park the truck, it has time to cool down. So maybe air is able to get in from other places (between seals, bearings, etc.?) . . . .

It seems that it’s only in the off-roading world that this becomes a problem because after running the differential hot, we could go in a very cold river for several minutes and this would cause a rapid decrease in temperature and potentially create a vacuum. . . .

Am I way off here, or does this make sense?
 

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Discussion Starter · #5 ·
If iar did not get out it would blow yer axle seals and gear oil out on the brakes.
If it needs to take air in it can to a certain point,if it draws air too fast it will close.
It must take in air reeeeealy slow cuz when I barely try sucking air through it, it seems like there is only resistance. . . .
 

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This thread brings a whole lotta blowing and sucking
 

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Discussion Starter · #7 ·

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Look in cheap trick threads for diff air breather mod? Did it for less than $10.
 

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Discussion Starter · #9 ·
Look in cheap trick threads for diff air breather mod? Did it for less than $10.
Yes, I did a seach for this subject but I didn't find an answer to this question. . .

I already have an extended breather installed front and rear, but my concern was discovering that the breather cap doesn't actually allow air in. . . . I just don't understand how the diff can be relieved of that vaccuum caused by going from very hot to cold in a short time.
 

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I think what your looking for is beyond my knowledge? Best of luck?
 

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This many words typed over a futhermucking BREATHER EXTENSION?!?!?!?!?! iS THIS REALLY WHAT WE'VE COME TO NOW? :(
 

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if you are that worried about it put a filter inline remove the factory 'cap' and be done with it. I would be more worried about having a 8" ring gear in a heavy rig than how much air a breather lets in.
 

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I have a different theory on what happens!

I have not looked at the Tacoma seals to check that it applies here, but most automotive oils seals I've seen have kind of "J" profile lips to them. They are designed to keep stuff in more than keep stuff out. Hence they do not work right if you were to put them in backwards.

Consider this: Excess pressure to the left of the J presses the lip harder against the shaft, improving the seal. Excess pressure to the right of the J tends to lift the lip from the shaft, allowing air in if the pressure difference is high enough. If the pressure difference gets too high the other way, things get nasty hence the breathers are installed.

I think you are right. If you extend the breathers you want to replace them with filters. This would additionally reduce any suction at the seals when the diff is cooled even if the breathers did allow restricted reverse flow. You would be removing the slight vacuum due to the restriction.

But on the other hand, I believe you don't need to worry about it too much in a typical water crossing, only if you get stuck good. I can't prove this or anything, but I think there is a hefty chunk of hot metal and oil there, and it takes a while to cool it appreciably even in ice-melt. The gears are what generate the heat and they are not exactly in perfect thermal contact to the outside. I know in air it takes several hours or more to cool some.
 

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I think it's just 'KARMA'. Your truck is just rejecting you because it's not impressed at all with your sucking and blowing! It really is looking for some serious performance form you or you're out!

CAN I HAVE A TRY!:D
 

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Discussion Starter · #17 ·
I would be more worried about having a 8" ring gear in a heavy rig than how much air a breather lets in.
I agree! . . . That's one of the reasons I am hesitant to go full-float in the rear right now. . . . I don't know if it's worth putting $800 into that axle if the R&P is still going to be the major weak point. . . .
 

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Discussion Starter · #19 ·
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