Diff breather

[Stumpalama]

The stock setup has its limits and it's known to allow water in. I ran a vent hose from my rear axle (I tied it to the brake line) up along the frame rail, I spliced in both my trans and T-case to that line, spliced in the front diff breather and ran it up on the firewall as high as it could go. I topped it off with an in-line fuel filter and to that I attched a short piece of tubing facing down so gravity won't feed it crud as the years go by. Problem solved.

See post #16

 

[jozlod]

It's pretty simple: Get a wad of 8mm or so vacuum hose a few T-fittings and some small zip ties. Remove the caps from the axle breathers, slip the hose over the nipple and secure with a ziptie. Run the hose along the brake line, securing with the zip ties toward the differential then use the soft brake line to run it up to the frame and leave some extra hose to connect to the hose coming from the rear.

For the trans/transfer I did the same thing (without removing either of them) using a T-fitting to join the hoses then fish a single hose over the transmission to the right frame rail and secure the the fuel line with zip ties. Now you can bring the hose from the rear diff breather forward by running it the same way as the front, using the soft brake line, to run it up to the frame and run it along the fuel line and T it to the trans/transfer hose and run it to the front hose from the front axle. Use a T to connect them and run the hose up the fire wall to the highest point you can. You can also run it into the cab if you like.

I used old brake bleeders I had laying around on the axles (they thread right in to the breather thread) and used one of the removed diff breathers at the top of the hose at the firewall to keep stuff out of the hose. I set this up 10 years ago and it's still working with no issues and I've done some deep crossings.
I did this for my FJ40, FJ62 and LX450.

HTH

thanks for the indepth description.
I'm about to do all my breathers, is good to know you've had yours like this for ages with no problems, cheers.

 

[Stumpalama]

I'm glad you found it worthwhile. I'm happy to to share some of the knowledge I've gathered. I especially like that the brake bleeders fit the axle breather hole. It makes for a nice barbed fitting for the hose.
Good luck with your work.

 

[ntsqd]

snippage
Why? If it is proven that positive pressure is what causes axle seal failure and subsequent gear oil-moly soup why would you introduce more?

Source, please. I've never seen it proven.
My own inner seals have failed because of poor alignment of the knuckle to the housing, which caused the inner axle to wear the seal on one side only.

And, just to be clear, I also think 10 psi is too much. Regulate that down to a couple psi and I'd go with it.

 

[Stumpalama]

Source, please. I've never seen it proven.
My own inner seals have failed because of poor alignment of the knuckle to the housing, which caused the inner axle to wear the seal on one side only.

And, just to be clear, I also think 10 psi is too much. Regulate that down to a couple psi and I'd go with it.

Post #4 of this thread demonstrates an extreme result of positive pressure in an axle housing. This was one of many, many threads discussing positive pressure and leaking seals. Certainly enough where the correlation cannot be discounted.
"It must have been a vacuum or you would have had gearlube spray all over you. My friend's 4Runner had a completely blocked breather on the rear diff. I pulled the drainplug and it shot out, I couldn't get the plug out fast enough, it sprayed ~10' in each direction, seriously, it was under a ton of pressure. That was when we found the breather totally rusted/clogged. We were replacing the rear axle seals, since they were leaking, well no wonder with that kind of pressure in there, I couldn't believe they didn't leak more, darn good seals."

A search revealed a multitude of threads referencing clogged diff breather and leaking axle seals.
So perhaps "proven" was somewhat poor word choice. Lets say "there seems to be an significant number of instances where a clogged breather was identified when investigating a leaking axle seal".
Either way, it seems positive pressure is to be avoided and thus a reason for a diff breather... would you agree?

Again, I ask, why introduce another "system" that requires regulation or something else to go wrong when atmospheric pressure seems to be the ideal environment?

 

[ntsqd]

I haven't done anything about a little positive pressure in the axle housings because I've yet to devise a simple way to achieve it. A couple psi is all that would be needed. Your quote of a post above "I pulled the drainplug and it shot out, I couldn't get the plug out fast enough, it sprayed ~10' in each direction" is clearly more than that. As usual, too much of something can be just as bad as too little. But that shouldn't be cause to avoid something. I know what just running the blower fan in the cab can do for keeping the dust out. Same principle, different location.

 

[Stumpalama]

I guess my question is still "why?" Or maybe better stated: "to what end?" If properly extended breather tubes prevent water and dust intrusion into the axle housing why add pressure? What value does the positive pressure add? I am not posing this as a rhetorical question, if there is a reason I have not considered I would like to learn about it.

 

[ntsqd]

Out here on the lower Left Coast I don't see much advantage because stream crossings are rare. In locations where they are more common if there is any tendency to leak, for any reason, then a little positive pressure will blow out of the seal/gap/leaking breather hose/etc. rather than allowing water in. Same reason for running the fan on high in dusty situations, air blows out of any leaks rather than allowing dust in. A friend with a very unusual 4x4 F-600 based camp machine uses two electric radiator fans to slightly pressurize the camper box. Running them in dusty conditions keeps the dust from getting in (fan intake is way up high out of most any dust).

 

[Stumpalama]

I can see the rationale for positive pressure in a cab... We use it on warships for counter CBRN (Chem, Bio, Radiation, Nuke). However, again axles are pretty tight so a good, simple, extended breather setup works great. Having done the majority of my wheeling in the PNW, I made MANY water crossings and have had zero evidence of water in my axles or trans/x-fer.

 

[ntsqd]

So you're against it, fine. It was only a suggestion and not on my must-do list.

 

[Hotrods65]

A bit late to this thread but thought I'd add a bit of info.
Just a quick comment on positive pressure in the diff housings, if you have arb air lockers it will fill the air lines with oil and push it out the valve breathers on the compressor. Your lockers won't engage/dis-engage properly.
I'm reading this thread as I looking to run new breather/lines as my rear breather was blocked and caused my locker air line to fill with oil.
Cheers

 

[Stumpalama]

A bit late to this thread but thought I'd add a bit of info.
Just a quick comment on positive pressure in the diff housings, if you have arb air lockers it will fill the air lines with oil and push it out the valve breathers on the compressor. Your lockers won't engage/dis-engage properly.
I'm reading this thread as I looking to run new breather/lines as my rear breather was blocked and caused my locker air line to fill with oil.
Cheers

That's good info.

Cheers,
Stump

 

[ntsqd]

At my proposed couple psi this should be a non-issue. If it is not then it's well past time to replace the ARB's seals.

 

[Hotrods65]

With the blocked breather it's a slow gradual process over a long period of time, the line gradually fills. Any pressure would cause this to happen imo. This is worth a read,
http://www.cruiseroutfitters.com/tech_ARB_troubleshoot.html

 

[ntsqd]

Does sound like a less viable option when fitted with ARB's. The simple solution, were one determined to do it anyway, would be for the ARB line to have the same or slightly more pressure than the diff does. The only simple method of achieving this that jumps to mind is that a low pressure regulator (as a guess, <10psi) be T'd into the ARB line and a calibrated "leak" be introduced to the line inside the diff. Not sure that's a great idea, but it is one.

Like I've maintained, it is an idea for consideration, not a must-do.

 

[Stumpalama]

anything that is going to provide pressure must 1) have a source, either electric or engine driven or 2) electric. you could have an air tank, but then you must have regulators for each system. Forgetting about what effect partial pressure may have on an ARB locker, that is waaay complicated for a very simple solution. "Rube Goldberg" comes to mind.

 

[NMC_EXP]

Found this thread while searching for info on extended breather lines.

Don't know that it matters as to how a differential, transfer case or transmission is vented, but here is the why a gearbox with EP gear lube should be vented:

You've noticed the rotten egg smell when you remove the fill plug. What you're smelling is the gas that is generated by the EP additives in gear lube. EP additives are designed to break down and form a coating on gear wear surfaces. The gas is a byproduct.

Part of the pressure rise in gearbox is due to heat. But most of it is a result of the gas that is generated while the gearbox is working.

Some shaft seals are designed to work with a specific amount of pressure on on side or the other. If the gear box in question was vented at the factory, then the seals were designed to work at atmospheric pressure. Pressurizing a seal designed to work at 0 PSIG is probably a bad idea.

Regards

Jim

 

[ntsqd]

Again, the idea is to maintain a couple psi only. Not 100 psi or more. Just enough that any leak do to wear etc. has air coming out of it, not water going in.
As to it being a Rube Goldberg, I haven't implemented it because I haven't yet found a simple way to do it. When I do, I probably will implement it.

 

[lehiguy]

I have a simple philosophy for this topic; keep the oil in and all other things out.