What features would you want to see in a differential/transmission/transfer breather?

[Hatsuwr]

I was planning on extending my vents up to the engine bay, and figured I'd improve the inlet a bit (some of my caps were stuck). A particulate filter is the first thing that comes to mind, but since I am in such a humid area, I think a desiccant would be good as well. I don't really want four separate ones, so I'd make a manifold for them all to connect. To prevent cross-contamination, I was thinking about having each inlet in a little well with individual baffles, and an oil mist filter on top.

Here's a realllly basic sketch of what I had in mind. The inlets would be in a square instead of a line. What other features would you add?

Bonus picture of the forbidden frappuccino:

 

[Dirt J]

Story behind the milkshake.

Just ordered ARB ripoff version on eBay FWIW.

 

[Hatsuwr]

Story behind the milkshake.

That was a '96 ZJ I bought around a decade ago. I'm pretty sure it wasn't from me driving through water, and I doubt humidity alone would have caused it, especially in the short time I had it before this picture was taken. Guessing the old owner had a little too much fun. Still, it drove probably at least a few thousand miles like that and was in surprisingly good condition. Still going strong too.

 

[Helipilot]

I ordered the ARB unit, mounted it high on the firewall and have not had any issues. I also recently checked the diffs, xmsn and xfr, all clean and I am based in Arkansas with the humidity issues we all are familiar with. Also have the same unit in my '77 FJ40, again no issues. Good luck on your project!

 

[RapidRob]

I'd agree, just buy the ARB, mount it high on the firewall, and send it.
I don't think significant airborne humidity will work its way in through the lines.
And you'll save lot of time. Just my 2Cents.

 

[Hatsuwr]

I don't think significant airborne humidity will work its way in through the lines.
And you'll save lot of time. Just my 2Cents.

Not too worried about the time, I like projects like this.

And I'm curious about the water contamination from humidity. Most UOAs I've seen for these have a water detection threshold which I believe is above where you would start seeing extra wear. The more sensitive test costs extra at most places, and it seems like most people don't bother. I wrote to a few testing labs to see if they can share any info about the results they've had for their more sensitive water contamination tests in automotive applications.

 

[Dirt J]

The factory lines have a one-way breather on the end that would address this, right?

 

[Hatsuwr]

The factory lines have a one-way breather on the end that would address this, right?

I'd think that air would get in fairly easily through the seals even if it doesn't through the breather, but I have no idea how much vacuum those would maintain. Maybe I should get an extra fill plug and throw on a pressure sensor for a few rides.

Either way though, the OEM breather cap not allowing easy vacuum relief can lead to water ingress via the seals when submerged, since the temperature drops fast enough to cause a decently high vacuum.

 

[Dirt J]

I disagree on air getting in "fairly easily" via the seals. The seals work well enough to keep fluids in and out. But I don't know enough about fluid dynamics (gas vs liquid) to really say.

And yes, humidity definitely did not create that Grand Cherokee milkshake. Be careful you aren't creating more problems than you "solve".

 

[Hatsuwr]

Would maintaining a vacuum be desirable though? There's obviously a downside regarding water crossing. I could see a potential benefit in reducing leaking past the seals when the vehicle is sitting... But it seems like that would be a pretty marginal consideration.

If a slight vacuum was wanted, it would be be pretty easy to achieve with a check valve — using the cracking pressure to create some vacuum, but allowing controlled air entry through the breather once it exceeds a certain level rather than having air/water forced in through the seals instead.

 

[x8o8drifter]

If there was water coming in through the seals you have worse problems to worry about fixing first.
And it wasn't humidity.

What you or the PO probably did was submerge the factory one and that let the water in.
Or there's a crack/leak in the line/diff mount.
This video shows you the system. 2:48 shows just how low that breather is.

You said "I'm pretty sure it wasn't from me driving through water".
How deep was the water?
Anything that sticks the pumpkin under water has the risk of that happening.

 

[Hatsuwr]

If there was water coming in through the seals you have worse problems to worry about fixing first.
And it wasn't humidity.

What you or the PO probably did was submerge the factory one and that let the water in.
Or there's a crack/leak in the line/diff mount.
This video shows you the system. 2:48 shows just how low that breather is.

You said "I'm pretty sure it wasn't from me driving through water".
How deep was the water?
Anything that sticks the pumpkin under water has the risk of that happening.

That picture is from like a decade ago. It's not really there to prove a point about anything, just a bit funny and related. I don't think I drove through any water before taking that picture, the uncertainty was just because it was so long ago.

 

[Jack90210]

Any air-borne water vapor that makes its way down the breather tube will readily evaporate at the first drive long enough to facilitate a normal fluid temperature increase.

Good point about the vacuum, but this is exactly the reason why the OEM breather has a valve.