Axle Vents

[Swamp Donkey]

Good point about the transfer case.. I wasn't even thinking about that. Would be kind of dumb to take the time to extend the vents on the axles, only to leave the transfer case stock. So I would need to run 4 vent lines up above the "water line," instead of 3. Good to know

The transmission and transfer case are already vented to the intake stack on the M939 series trucks.

 

[BigDawg41]

WRONG about the MOD being POINTLESS, the axle vent ONLY breathes one way "out", as pressure builds and the vent is SUPPOSED to dump the extra pressure, it dumps the pressure, then the axle cools down, the pressure drops, to where there COULD be a bit of vacuum, this will tend to draw dust, ect to/through the seal, no different then a constant pressure on the seal that will tend to try to force oil out, oil and dust = valve grind compound or in this case seal wear. the HOT pressurized vented air is oily, it makes the axle vent oily, which in turn dust sticks to, so in time it takes MORE pressure to pop the axle vent, holding more pressure in the axle, and in time, things only get worse, NOT BETTER.

Unless you only ran a few pounds (10 or less, more like 5) of air to test the vents, YOU WASTED your time and shop air.

The axle vent on our trucks is there fore ONE REASON and ONLY one reason, that is for amphibious operation, to help keeping water out of the rears, this is the same reason for the rear grease hubs.

Ah ha! Thanks for that explanation.When I drive my truck,the axles hold pressure for days when I go to check the fluid levels.It makes sense now as to why all my axles lately seem to be pushing more oil out the pinion seals/flanges and steering dust boots.I know I need to repair them eventually but for now I will try to clean my axle vents or replace them to slow the leaks.I don't do any fording or mudding so I will hold off on the awesome axle vent MOD idea for now.

 

[brazengoat06]

ALL the axles have axle vents, on the front, air will be drawn in through the axle seal, oil out, the grease will be no where near it, also while we are on "axle" vents, the transfer case has the SAME vent as well as the manual transmission, these ALSO have the SAME issues as the axle vents.

The "VENT MOD" is due to the VENT issues, there would be no need if there were not the vent issues, the number ONE cause of axle, and to a lesser extent transmission/transfer seal leakage is a BAD vent.

As the OLD and SORTA WISE Wreckerman would say "your dog, beat it as you see fit"

That's making more sense thank you! However it brings up the question if one doesn't "mod" how much depth can those axles take? With the fording kit it adds pressure to the axles so if these valves are designed to hold a regulated pressure on the axles then why are people removing them? And yes just talking about axles not anything else. Thanks!

 

[JohnnyBM931A2]

The transmission and transfer case are already vented to the intake stack on the M939 series trucks.

lol. Ok nevermind then

 

[dawico]

That's making more sense thank you! However it brings up the question if one doesn't "mod" how much depth can those axles take? With the fording kit it adds pressure to the axles so if these valves are designed to hold a regulated pressure on the axles then why are people removing them? And yes just talking about axles not anything else. Thanks!

Too much pressure can be held in if the vent doesn't operate properly or gets plugged.

The little pressure the vents hold in is to fight water intrusion while submerged. That probably isn't an issue for most of us.

Mine have all been removed and the lines plumbed into the intake. Now to fix all the axle leaks. Not saying they are directly related but zero axle pressure makes sense to me.

 

[73m819]

This thread seems to have moved from a properly functioning vent to mods for fording. Is mudding and being under water your use or having a working vent? Venting goes both ways, so why a check?

Very true on the thread movement, the reason is a good vent does not stay good very long, I have pulled vents from trucks that has not been run in a week, every time there is a pressure release, and every time the reason the vent got pulled was because on a seal seep, either at the hub OR the pinion.

The vents on our trucks ARE one way operation and that is OUT, even if the stock vent works, the axle, ect CAN NOT BREATH.

The MOD has NOTHING to do with mudding, fording, ect. The MOD is put in place to PREVENT seal leakage which in turn prevents oil on the brake shoes/drums, helps to prevents a seal from leaking where it will pick up dust (not mud) which in turn turns into a oily grit which WILL ware a grove in the sealing surface.

People would NOT go though the hassle of climbing under truck, fighting grease, dirt, ect to installing a vent system if it were not needed.

AGAIN the NUMBER ONE cause of axle, and transfer case seal leakage IS a BAD VENT. transmission some what also

 

[tobyS]

A sintered air fitting, 1/2" pipe thread, new under $10, will keep the dirt out and most of the oil in (eventually some shows in the dirt that accumulates) and be rugged enough to handle a mount to the axle. They come in a cone shape and flat. The cone has more surface area.

Ron, wouldn't the CTIS system have a lot to do with a positive pressure? So if one does not have a functioning CTIS then that may not be an issue and a 2 way vent (filtered) would work properly.

 

[73m819]

The CTIS uses SPECIAL hub seals that ARE designed to hold the pressure, while non CTIS seals are designer to hold oil in/dirt out but are NOT pressure seals. This is why CTIS seals are so much more EXPENSEVE the non CTIS seals.

I am not sure how the CTIS is internally plumbed, The leaking seals issue due to the vent issue has been a problem as long as I can remember, when I had my 52 m52 in CA. long before I found SS, I had the vent issue, some old MVer that I had met (old them I am and that IS old) suggested the venting system along with the filter, said when "he was in" this was what they did to keep oil out of the brakes, so I have seen that the vent system works and became a believer so I try to pass it on and point out ALL the hassle (pulling drum, ect.) it saves.

 

[plode]

Anyone know off hand what thread the axle vents are? Been meaning to add barbed fittings to the "bring home from Home Depot" list.

 

[rhurey]

1/8" npt

 

[plode]

1/8" npt

Of course our local Home Depot doesn't have 1/8" NPT barbed fittings. Will have to reduce a larger one down.

 

[tobyS]

Here is McMaster-Carr for barbed hose fittings;

http://www.mcmaster.com/#standard-barbed-hose-fittings/=y9m20f

And here is a sintered fitting;

http://www.mcmaster.com/#4450k1/=y9m0rt

 

[plode]

Finally got around to putting all of this on the truck. Used 1/4" NPT 1/8" barbed fittings for the axles, tee'd the rear two axles together, then ran a line from the front under the truck to around where the intake stack is. I used rubber vacuum line made by Gates that I got on Amazon. Figured it would be okay for a vent line. Did the same from the rear up to the intake stack area.

Now have to get another tee, and I'm going to run the line up the intake stack and bend it around 180 degrees(so water doesn't get in) and put a sintered exhaust fitting in it to keep the wasps out. Still a little concerned with it being out in the weather and water intrusion...should I run it into the cab?

I was also thinking about putting a couple valves in so I could possibly hook up a regulator and send 1.5-2psi into the axles to keep water out if I ford the truck. Where can I get such a regulator that can manage such little pressure with a bit of accuracy- I know cheesy HF regulators, 1/16th of a turn on the valve and you're increasing pressure by 5psi. I don't want to put that much into the axles.

Also, sort of unrelated, but are the transmission and transfer case vents already running into the intake piping? If so I won't have to mess with them.

 

[Artisan]

Finally got around to putting all of this on the truck. Used 1/4" NPT 1/8" barbed fittings for the axles, tee'd the rear two axles together, then ran a line from the front under the truck to around where the intake stack is. I used rubber vacuum line made by Gates that I got on Amazon. Figured it would be okay for a vent line. Did the same from the rear up to the intake stack area.

Now have to get another tee, and I'm going to run the line up the intake stack and bend it around 180 degrees(so water doesn't get in) and put a sintered exhaust fitting in it to keep the wasps out. Still a little concerned with it being out in the weather and water intrusion...should I run it into the cab?

I was also thinking about putting a couple valves in so I could possibly hook up a regulator and send 1.5-2psi into the axles to keep water out if I ford the truck. Where can I get such a regulator that can manage such little pressure with a bit of accuracy- I know cheesy HF regulators, 1/16th of a turn on the valve and you're increasing pressure by 5psi. I don't want to put that much into the axles.

Also, sort of unrelated, but are the transmission and transfer case vents already running into the intake piping? If so I won't have to mess with them.

Sure would like to see some pics of your handy work there plodester...

 

[plode]

Sure would like to see some pics of your handy work there plodester...

I'll have to crawl under the truck again and snap some pictures. It's nothing crazy or elaborate. Just did what is needed to get the job done. I'm a volunteer firefighter on a barrier island.
During Hurricane Sandy our town only had a M109 with none of the proper preparations for fording or anything. It broke down several times during the storm, leaving members of the fire department and police department stranded on the island.
The city has since acquired several M923's and M925's, including an M925 dedicated for the fire department. I'm assisting in painting/building that truck so it is ready for any storms(ready for fording, somewhat) since I seem to be the only one knowledgeable about their capabilities and their flaws. The rest of the trucks the city has, I'm sure will go unmodified, and people unfamiliar with them and their operation will drive them into deep water and will have to deal with the consequences of that... Unless the town hires me, I can't go spending all of my time on their trucks, prepping them for storm duty- that would be a full time job, seriously.

I don't plan on using my personal truck for anything too "business" related, but merely for transportation on/off the island in a storm- which may have to do some fording depending on the degree of flooding- during sandy the road into the town, during the peak of the storm was at around 30 inches deep- which supposedly the M923 can do "stock". And of course the trucks' normal uses- recovery of friends stuck trucks, parades, car shows etc.

 

[Artisan]

After reading that, something popped into my mind.
I wonder if a guy could be proactive and think outside
the box and turn the axle vent into positive pressure
system where w/ the flick of a switch you could put low
air pressure INTO the axle when you know your going fording
to attempt to keep water out? Certainly you will not have heat issues
cause your in water. A pressure regulator limiting the pressure
to .5 lbs would allow up to 4.9' of head of water.

 

[plode]

After reading that, something popped into my mind.
I wonder if a guy could be proactive and think outside
the box and turn the axle vent into positive pressure
system where w/ the flick of a switch you could put low
air pressure INTO the axle when you know your going fording
to keep water out? Certainly you will not have heat issues
cause your in water. A pressure regulator limiting the pressure
to .5 lbs would allow up to 4.9' of head of water.

This is my question about a reliable, accurate regulator in my previous post. I'd love to close a valve that shuts off the vent to atmosphere and another that pressurizes the axles a tiny bit to keep the water out.
Problem is, I need a regulator, and need to route the valves somewhere they are accessible.

 

[tobyS]

A gas pressure regulator for torch fuel is rather low pressure, even has high side and low side gauges in the ranges you are looking for.

 

[Artisan]

A pressure regulator that is reliable should be pretty easy.
For instance in seconds I found THIS at McMaster. Looks
like it is good down to 32* there are probably some better
units out there.

 

[tobyS]

A pressure regulator that is reliable should be pretty easy.
For instance in seconds I found THIS at McMaster. Looks
like it is good down to 32* there are probably some better
units out there.

Did you happen to look at the price?