Air intake stack vents and bypassing axles

I have been doing some research regarding vents from axles, fuel tank, Trans and T case.

First I will say I have a water fording kit on my M-923 (Marine truck).

I vented the 3 axles up to the air intake cap. I know there is supposed to be pressure from the inside of the hub to prevent water from coming in. However, I don't trust the vent caps and they can get stuck if dirty. Also water can get into the axles. I did notice a good amount of pressure release from the vent hole when I took the vents off. I'm not sure if lockers increase axle pressure but there seemed to be a lot of pressure build up. If I want to water ford I'll put on the fording kit on to give it a little inner pressure. This way the seals will last longer and water will not get in to the axles. I recommend doing this to all military trucks. If you don't have a fording kit you can always put a cap on the end of the vent hose when you water ford. Also don't forget to plug the bell housing. I plan on adding a ball valve with elbow to it. That way I don't have to screw in the bolt before water fording.

Next, I was thinking of venting the T case, trans and the 2 fuel vents. All of these vent vapors and possibly oils into the air intake stack. Oil and fuel can be accumulating in the air box causing a "run away" motor if to much builds up and gets sucked into the motor. This would only happen if the T case, trans or fuel was overfilled or if the fording kit was left on to build up pressure. I was thinking of running these vent lines up the air intake stack and allowing them to vent there into a container or allowing it to just drip to the ground.

Is there any flaw to these thoughts?

I removed the vents from mine, as well. Each gave a healthy breath as I removed them.

When I blow threw the vents, it takes about 1 or 2 psi to make them open. Trying to suck on them (tasty!) Does nothing. No air comes in.

I haven't put them on a vacuum pump to see if air can actually get back in.

The question. ... are these supposed to work this way? (Negative air pressure in the axle)

RustyM923 said:

I removed the vents from mine, as well. Each gave a healthy breath as I removed them.

When I blow threw the vents, it takes about 1 or 2 psi to make them open. Trying to suck on them (tasty!) Does nothing. No air comes in.

I haven't put them on a vacuum pump to see if air can actually get back in.

The question. ... are these supposed to work this way? (Negative air pressure in the axle)

Click to expand...

I believe they are supposed to work this way but I don't trust a 3 dollar piece to function when it gets dirty or clogged over time. And, the added pressure on the seals will make them leak sooner. I don't water ford much and when I go in the mud its usually no more than 2 or 3 feet. I think with the heat build up and the length of hose the gases have to vent will put enough pressure on the seals anyway. If I'm really worried about it I would put my fording kit on for additional pressure or cap the vent when fording. Also remember the pressure of water increases the deeper you go. I don't think sucking on it with air can compare to water pressure at about 4 or 5 ft deep. Pressure from the water will come from depth and motion of the water as you travel in it. A better way to check it would be to attach the vent to a capped water tight bottle. Then put it under 5 ft of water and shake it violently. If water doesn't get in to the bottle you're good.

TacticalDoc said:

I believe they are supposed to work this way but I don't trust a 3 dollar piece to function when it gets dirty or clogged over time. And, the added pressure on the seals will make them leak sooner. I don't water ford much and when I go in the mud its usually no more than 2 or 3 feet. I think with the heat build up and the length of hose the gases have to vent will put enough pressure on the seals anyway. If I'm really worried about it I would put my fording kit on for additional pressure or cap the vent when fording. Also remember the pressure of water increases the deeper you go. I don't think sucking on it with air can compare to water pressure at about 4 or 5 ft deep. Pressure from the water will come from depth and motion of the water as you travel in it. A better way to check it would be to attach the vent to a capped water tight bottle. Then put it under 5 ft of water and shake it violently. If water doesn't get in to the bottle you're good.

Click to expand...

Heat increases air pressure. If your axle is at zero psi, in a closed system, the pressure will increase above zero as things heat up (positive pressure in the axle). The vents that I pulled off would only let that get to about 1psi before they vented. If the axle inside heated to more than the temp to reach 1psi, the excess would be vented...

Anyway, what happens when it cools? It would seem that if you vented 3 psi of pressure, when the axle cooled to ambient temp, the pressure inside would be negative 3psi. I suppose that might sound good, but...when you dunk that piece of steel in the water, the axle instantly cools and (might) put negative pressure on the seals, causing water to get in.

I'm with you on modifying it. I will likely just put hose barbs and run the vents somewhere up high to maintain zero PSI in the axles, despite temp changes.

Does anyone else's vent caps act like mine? (release pressure only)

I realy don't think that the axles and all the heat in the gear lube with housing will cool instantly.

Floridianson said:

I realy don't think that the axles and all the heat in the gear lube with housing will cool instantly.

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Good point. Poor choice of words on my part. The axle will not cool instantly, but it will cool when being run under water.

Didn't think about the cooling but I guess over time it would. There is no down side to venting them through a gas rated tube to the cab or air intake mushroom.

is there any benefit to running negative pressure in the axles? (specifically with regard to leaks)

RustyM923 said:

is there any benefit to running negative pressure in the axles? (specifically with regard to leaks)

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if you water ford with neg pressure in the axle it could suck water into the axle.. The best thing is to have no pressure unless you want to water ford. If you bypass the axles you can do this by capping the end or if you have a fording kit you can just put it on and it will give you enough positive pressure.

Anyone have any input on venting the T case, trans and the 2 fuel vents to prevent oils going into the air box?

TD, your venting ideas have been posted many many times.

It's no revelation.

doghead said:

TD, your venting ideas have been posted many many times.

It's no revelation.

Click to expand...

that's why Im asking about venting the T case, trans and the 2 fuel vents to prevent oils going into the air box? Never got answers to this. But thanks for your very helpful input.

I vented my trans and transfer case to my aircleaner housing on my cargo deuce, ive put 5000 miles on it since, the multi fuel hasent run away yet.

440 search results for "transfercase vent".

http://www.steelsoldiers.com/showthread.php?76914-axle-vent-modification

RAYZER said:

I vented my trans and transfer case to my aircleaner housing on my cargo deuce, ive put 5000 miles on it since, the multi fuel hasent run away yet.

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On the deuce it his that same vents as on the axles if I remember correctly. on the 5 tons they have a hoses going to the air intake already. you did the same thing but I think its still better to have it drain in another place because I have had oil drip into my air box and if it didn't leak out it would have built up and gotten sucked in to the motor

doghead said:

440 search results for "transfercase vent".

http://www.steelsoldiers.com/showthread.php?76914-axle-vent-modification

Click to expand...

that's from 2011 maybe others did something different in the 2 years since that post...always good to check more current things that my be happening or maybe new members want to review it. So, I pulled my thoughts from the research I did and put it together for new members and to check if my thinking is correct.

Lets not forget to capitalize now.

That's not new, but we still do it.

I put vent tubing on all three axel"s and run to top of intake stack and put a charging port on so I can pressurise the axel"s when I want.

Are we in school or what? I think we are all here because we have a common interest, do useless or degrading posts help recruit new members or public acceptance? Seems like some people have too much time on their hands....

We have standards(6-8th grade English), and we will not lower them.

Just so nobody gets offended, no quotes were added to that post but I don't think it was necessary to single anyone out.