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Connecting all the breather tubes to a single outlet?

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norgeek

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Sorry for the overcomplicated post - TL;DR: thread title, yey or ney?

I've tried to (re)search, but results are only making me confused.

I'd like to extend the breather tubes on my V2500 6.2 Suburban, preferably high enough to match my snorkel intake height. That would be front and rear differentials, transmission and transfer case, right?

What I would like to do is a common breather line, starting at the front, connecting to stuff with T's coming rearwards, and then going up through the cargo hold to a roof-height outlet with a fuel filter somewhere up there. I'm thinking that I should probably opt for an external vent (like on boats), rather than vent fumes into to interior. It's closed off from the passenger compartment, but still..

But after reading about more than fumes making their way out through these breathers I'm having second thoughts. Especially certain threads about transfer cases ejecting oil even with the breather mounted high on the torpedo wall. I've seen several threads where someone has done the common breather tube thing, but never read how it turned out down the line.

Is there a real risk of oils mixing? And if so, is this an actual problem? (Kinda assuming it would be a problem.)

Come to think of it, the NP241 should use ATF just like the 4L80e, right? Would it be safe(er) to do two separate lines, one for the differentials and one for the transmissions?
 
Oh, wow. Definitely never ran across those things before, but they do appear to be quite perfect. Thank you!

Edit; Or are they that perfect? While they do seem to be the go-to solution in low-speed applications, people seem to be reporting issues with limited room for expansion with heat buildup. I frequently hit 70mph for hours at a time.. Others again are saying that ARB lockers are less happy about the pressure buildups. While I don't have them yet, I hope to get front and rear lockers next year.

That, and I'd kinda worry about them just appearing somewhat more fragile/exposed than half decent fuel line. Hmm. But I'll continue to look into that venue regardless :)
 
DON'T tie them together, you could have one of the vented items create a vacuum and start sucking fluid out of one or more of the others.
 
X2, I connected all mine together and it turned into a mess. Now I run separate lines for everything. You need to make absolutely sure there isn't any low spot in the breather at any point along it's route. Oil droplets in the vapor will collect in the low spots and eventually build up enough to close the vent. Once that happens, the pressure burps that oil all the way up the line. Having individual shorter runs has worked out better for me, especially with long hot summer freeway drives at 70mph. Make sure not to overfill any of them too.
 
I like the bellows type breathers. I've always been curious, can they be blown off from excessive pressure? If you overfill, let's say a tcase that is clocked or what have you, and its overfilled, what happens to the bellows breather, or seals if it doesn't blow off?
 
I do have my T-case and tranny on a shared vent line - routed up to the wiper motor. The only vacuum I can imagine would be running hot and then dunking a gearbox in a river. Even so, the vent line should be tied to air in the top of the box - not oil. Otherwise the vent line would have been spraying fluid before the vents were ever extended. It's been fine for years, AFAIK.

The front diff has a nice factory vent tied to the frame rail, so I just extended that one up near the top of the core support . I think I ran the rear diff along the fuel fill hose, so it's up in the quarter panel above the fuel door. If I ever get the whole interior swamped I'd best drain all the fluids anyway.

If you had a snorkel, you could run some vent lines up through the snorkel so they are actually above your roof line. It seems like fording at those depths presents much bigger issues than just vent lines, but vacuum line is cheap.
 
What about having all the vents tee into a header line that has both ends open? That would keep a vacuum from forming and drawing oil out of the other components.
 
I'm not sure I understand how one component could draw oil from another. If the vents are open to the air, it would take a hell of a suction to draw oil instead of just air, especially since most things only have one vent anyway. I guess if a component belched oil, it could go upstream into the next thing though.
 
Thanks for the influx of new replies, my instant email notification somehow forgot to notify me.

I'm also not sure I see how one device would suck oil from another device here unless you're at an "oooups :eek1:"-level of vehicle tilt. The breather openings should all be mounted somewhere oil shouldn't normally reach (unless overfilled), and unless the line up to free air is severely limited (low spot filled with cold sluggish oil, or too thin ID tubes) I don't see how any serious vacuum could form as it would rather suck air down than oil up.

Apart from suddenly supercooling the drivetrain with a bath, my understanding is that the thing with breather openings is to let pressure out (so it won't force oil through the seals and leak/break stuff).

And even in the event of sudden, significant vacuum, like taking a head-first red-hot dive into a river (which would be a rather bad idea for my turbo anyway) you'd mostly be subjecting the drivetrain to the same temperature changes. So, everything would be sucking at the same time, rather than one thing heating up and ejecting oil, and another thing cooling down and sucking the oil in.

Still, if I go with this, I'll do two independent lines, one for ATF and one for differential oil. And at that point it's not much extra fuss to simply do completely independent lines anyway I guess, depending on how I lead the ends to free air.

I could put the breather line inside the snorkel, but I'd rather not poke an extra hole it in. Besides, I think it's borderline undersized as it is, no need to make the engine work harder to take a breath. Outside of the snorkel just doesn't look as clean as I'd like it (which doesn't say much as my truck is a bit of a mess, aesthetically speaking), and I feel a certain trepidation towards mounting a direct line to my drive train internals that exposed to the elements.

And yes, extending the breathers up to hood-height would probably be sufficient. If I ever get in that deep I'll have drowned half the electronics in the car anyway. But if I'm doing something about it in the first place I'd rather overdo it; I can drive on as long as I have to without electronics, but how far will I get with watered-out oil? I have an ambition to drive this thing pretty far into rather remote areas (Mongolia tends to come up), so I'm trying to over-engineer whatever modifications I do.

cybrfire: From what I've read, blowing the bellows off is mostly related to leaky ARBs. A pretty significant "pop", apparently.. Without ARBs, the bellows (if good quality) appear to be solid enough to overpressurise the pumpkins until oil gets out elsewhere. There seems to exist a common advice to make a small slit at the top/end of the bellow with a sharp knife to allow excess pressure out while keeping water and debris out, but that seems a little risky.
 
I just ran each one up to the highest point in engine by (right beside wiper motor)

Been like that for years, no issues.

 
For reference, I ran a hose from my rear diff up to the frame rail and then all the way up under the hood near the air cleaner. I had fluid puking out the hose after several hours driving near Barstow in 90 degree weather. That's a long way for oil to travel uphill so I have to assume it was caused by some kind of buildup.

No matter what you do, make sure any oily vapor or bubbles can drain back down into the diff.
 
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