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Axle bellows

WaterH

WaterH

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This subject has cone up in several threads, most recently in hydro-Dynanmics. I didn’t want to muck up his build thread, but I’ve always had questions about these that would take some tests or some good math. The main question is do they work? That sounds simple, but when you think. It through, it gets complicated.

First, the idea is you put the bellows on your vent so no water or dirt gets in. The purpose of the vent is to relive pressure on your seals as the axle/T-case or transmission heats up or cools down. The purpose of the bellows is to expand and contract negating the need for a vent. Sounds great. No more tubes going up to a high part of your frame that could get ripped off. In theory, the whole vehicle could get submerged and you wouldn’t get water in your axles or gearboxes. (Sorry about your engine)

One of my thoughts is put a pipe plug in the vent. When I have mentioned this, people invariably say the pressure will cause the seals to blow out. Is this true? Anybody have experience with this? I have come across some axles that the vent was completely clogged with grime and the seals weren’t blown. What if you install the seal in such a way that it can’t blow out? (Some kind of keeper or pressed in from the back side) I have seen a seal cut a shaft. (Not an axle shaft) It didn’t cut it completely and I’m not saying it was due to air pressure, but that may be a possibility. I have a lawn mower gearbox on my tractor that has no vents. It get really hot and doesn’t blow seals or leak oil.

Setting all that aside, will the bellows work? To answer that question, we need to answer a few others first.

1. How much air is in an axle housing?
2. How much would that air expand from a temperature increase of say a 100 degrees?
3. How much would the pressure go up due to that expansion?
4. How much pressure is too much for the seals?
5. Finally, how much pressure would a typical bellows relieve?

If you really want to dig in to this, you could figure out how much the oil expands and ”pushes“ on the air in there, but I doubt it is enough to warrant consideration.

I would appreciate anybody that has gone to the trouble to figure this out to put some numbers to these questions.

This is one of those things where you would think “They are selling them, so they must do something”. I’m not so sure.
 
Oil expansion is definitely part of the equation... airation is also another.
Have you ever had a diff puke oil out of the breather? I have, and it wasn't over full, also ran the tube up into the box of the truck under the bed rail, so plenty high enough. Oil Expansion, air expansion, and airation all play their part. You have to take into account how much oil is in the diff just the same as you have to account for the air in there... if you can figure those equations, you can figure the rate/ amount of expansion, and get a bellows big enough to handle it in the worst case scenario. I think you're wasting your time trying to plug it for science. There's a reason it is atmospheric and not pressurized.
 
Yes waterhead if you plug the diff you will blow oil out the seals. Dust will collect on the puked oil and burn grooves into the sealing surface fucking it up. Any pressure on seals not designed for pressure is not good.

I use bellows on most of my gear boxes for my conveyors. They save the life of my seals by many times. In my application the standard breathers get plugged with dust and then the puke oil out the seals and the shafts get destroyed. With that said the volume of my gear boxes are tiny compared with an axle diff. The bellows would have to be a gallon in size to accommodate the heat and amount of airspace that’s in an axle. Imo not worth the trouble just route a hose to vent to atmosphere up high like everyone and call it a day.:flipoff2:

I pay about $400 each for bellows for my gear boxes. They are stupid expensive but the save me the trouble of having to reseal the stupid things every year.
 
Ive ran the trail gear bellowed plugs on probably 15 different differentials and have never had any issues.... ive also had a lot of trucls with no breather tubes... maybe they were cloged, maybe they fell off... I never looked and they never dripped any oil on the ground
 
FC4X4 said:
What's a $400 bellow look like?
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They are stupid expensive :homer:

IMG_8844.jpeg
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I believe JohnnyJ had them on his 4500 car and was blowing axle seals. Seemes to me he put a slice in them to allow extra expansion.

While that will work in a race or dry application, I think it would allow water in if you are in deep water.
 
I have the trailgear bellows on a 44, 14b, and 233 in an s10. No scientific experiments have been conducted. But everything leaks. I’ve done hub seals on the 14b at least twice over the years. I was staring at the 233 a couple days ago, thinking maybe I should bring it down and reseal it. The 44 always leaks out of the fill plug in a ruffstuff cover, I figure the threads don’t seal enough that it leaks there instead of blowing out a seal.

That said, I also put them on a 60, 14b, and 205 in a square body I’m currently working on. Not enough miles on it yet to determine anything.

I think what happens is the oil heats up and finds the path of least resistance to get out.
 
Tried the bellows on my RockJock 60’s in my old race car and it would blow the pinion seal out of the housing and dump the gear oil out. The surface area on the seal housing is huge because one of the big things about the RJ is using the same big pinion bearing on both sides of pinion. No seal retainer and none of the aftermarket billet or forged yokes have the dust cover. Axles build enough air pressure from heat expansion to just push the whole seal out of the pocket.
 
2big bronco said:
Ive ran the trail gear bellowed plugs on probably 15 different differentials and have never had any issues.... ive also had a lot of trucls with no breather tubes... maybe they were cloged, maybe they fell off... I never looked and they never dripped any oil on the ground
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The only problem I've had with those cheap ones is they split on the folds and you don't know it, I went back to 6' of tubing and the factory vent, one is mounted near my master cylinder, the other is in my gas door. no seepage.
 
Sterlingfire said:
Oil expansion is definitely part of the equation... airation is also another.
Have you ever had a diff puke oil out of the breather? I have, and it wasn't over full, also ran the tube up into the box of the truck under the bed rail, so plenty high enough. Oil Expansion, air expansion, and airation all play their part. You have to take into account how much oil is in the diff just the same as you have to account for the air in there... if you can figure those equations, you can figure the rate/ amount of expansion, and get a bellows big enough to handle it in the worst case scenario. I think you're wasting your time trying to plug it for science. There's a reason it is atmospheric and not pressurized.
Click to expand...

When you say airation, youre speaking of bubbles in the oil. I don’t believe that increases the total volume of the air and oil.

As far as oil expansion, I was under the impression that any liquid only can expand or contract a total of 4%. When you get a gearbox puking oil, I believe it splashes on the vent inside and than air pressure sends it out. It also could be some water is in there that is converting to gas. That would be a lot more than 4%.
 
ThePanzerFuhrer said:
It’s made for a really small box. Would not work for an axle. Your best bet is the tried and true run a hose up to the top of the frame and call it a day.
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How hot do your small gearboxes get? One of the helicopters I fly has a tail rotor gearbox with no vent. It gets around 180 degrees. It’s about 6” cube. They generally never leak.
 
Ironically i searched thru the other place for the bellows p/n. I ran into several threads started by guess who?
 
I used a bellows on a new HP D44 axle build and the seals blew out on a multi-day Mohave Road trip. After I replaced the seals, I ran breather hose up to the top of the firewall and used a generic lawn mower fuel filter to keep the dust out. No more blown seals.

Bellows work for some axles and not for others. Same bellows didn't blow the seals on my 8.8, but there is a lot more oil and a lot more open space in that axle. D44 holds 2 quarts, 8.8 holds 3.5 with my pinyon angle.
 
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BDK said:
I used a bellows on a new HP D44 axle build and the seals blew out on a multi-day Mohave Road trip. After I replaced the seals, I ran breather hose up to the top of the firewall and used a generic lawn mower fuel filter to keep the dust out. No more blown seals.

Bellows work for some axles and not for others. Same bellows didn't blow the seals on my 8.8, but there is a lot more oil and a lot more open space in that axle. D44 holds 2 quarts, 8.8 holds 3.5 with my pinyon angle.
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Were they from trail gear? The old place covers that TG bellows were very rigid and not flexible. Other than the arb incident i had no issues over 4 years of running the ones from polaris/artic cat.
 
WaterH said:
When you say airation, youre speaking of bubbles in the oil. I don’t believe that increases the total volume of the air and oil.

As far as oil expansion, I was under the impression that any liquid only can expand or contract a total of 4%. When you get a gearbox puking oil, I believe it splashes on the vent inside and than air pressure sends it out. It also could be some water is in there that is converting to gas. That would be a lot more than 4%.
Click to expand...
Yes that is exactly what airation is... while you are correct it doesn't increase the volume of oil or air, it raises the level of oil in the diff significantly, and the hotter it gets in there, the more the air expands and higher the level of fluid, and the closer to the vent it gets... now if you plug that all up, where is that pressure going to go? You even answered your own question by saying the air pressure(hmm i wonder where that's coming from??) Blows it out the vent... as i said, a bellows will work, but you need to know the volume of everything so you can get the right size one for the application... otherwise you'll be in the same boat, the air pressure(fucking expansion from heat lol) needs a place to go and will either blow out an axle seal or the pinion seal, whichever is the loosest.

For you guys that have had issues with a diff blowing out the bellows, do you know what the gear pattern looked like at install? I wonder if a tighter gear mesh will create more or less heat then a loose mesh? Maybe this is why some axles have no issues and some are the opposite.... also a front diff will have less oil in it then a rear, so maybe that helps too.
 
The bellows sure sounds like a great simple solution. It also sounds like you have to get the math perfect or just get lucky. I know I'm not lucky and the math part would just be making up numbers. Plus, I've got ARB's and a leak would make the bellows the same as a plug and goodby seals.

If running a hose up high and still getting oil, would it make sense to increase the size of the hose?
I wouldn't think people are getting a vent hose completely full of oil, but more like a small slug of oil, air, slug of oil, air. Seems like increasing the size of the hose would help reduce the surface tension of the oil and allow the air to pass it by.



Sterlingfire said:
For you guys that have had issues with a diff blowing out the bellows, do you know what the gear pattern looked like at install? I wonder if a tighter gear mesh will create more or less heat then a loose mesh? Maybe this is why some axles have no issues and some are the opposite.... also a front diff will have less oil in it then a rear, so maybe that helps too.
Click to expand...

Tighter gears will compress the oil more which creates more heat.

Ford 9" creates more heat than other diffs just due to the design and amount of gear contact. What is it called? Hypoid angle?
 
What I was really hoping for here was somebody post a link to a site where they have all this figured out for at least one common diff. But apparently it’s not been done. I do have an old Dana 44 in the shop. I guess I could fill it with scrap oil to determine it’s volume.

My gut tells me Panzer is right and an axle will need a gallon of bellows to be effective.
 
WaterH said:
What I was really hoping for here was somebody post a link to a site where they have all this figured out for at least one common diff. But apparently it’s not been done. I do have an old Dana 44 in the shop. I guess I could fill it with scrap oil to determine it’s volume.

My gut tells me Panzer is right and an axle will need a gallon of bellows to be effective.
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it looks to me the trail gear thing is way too stiff. It should be fully collapsed when axle is cold and be allowed to easily expand when the axle heats up.

Monday call tech support for these guys and see what they say. They should have the answers you’re looking for. They make one that is 7” in Diameter.

www.gitsmfg.com

Expansion Chambers - GITS

The Gits Expansion Chamber absorbs surges and expansion of gas or fluids in a closed system. Expansion is provided by the movement of a tough, elastic diaphragm enclosed in a protective steel chamber. On machines with lip-type seals it reduces pressure build-up which can cause seal failure. At...
www.gitsmfg.com www.gitsmfg.com
 
WaterH said:
I did some searching and found this.

www.pirate4x4.com

A trick for keeping water out of the axle

www.pirate4x4.com www.pirate4x4.com

JR was the thread starter. I know he’s on here, but I don’t think he checks in much. I wonder if he was happy with the pressurized axles. Makes me think the pipe plug is not such a bad idea.
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For the millionth time your seals will get wrecked in no time. That thread is from 2009. If it worked you would have heard about it. Unless you positively hold the seals in and use the correct pressure rated seals it’s a no go.
 
WaterH said:
I did some searching and found this.

www.pirate4x4.com

A trick for keeping water out of the axle

www.pirate4x4.com www.pirate4x4.com

JR was the thread starter. I know he’s on here, but I don’t think he checks in much. I wonder if he was happy with the pressurized axles. Makes me think the pipe plug is not such a bad idea.
Click to expand...

ThePanzerFuhrer said:
For the millionth time your seals will get wrecked in no time. That thread is from 2009. If it worked you would have heard about it. Unless you positively hold the seals in and use the correct pressure rated seals it’s a no go.
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This. There are some industrial axles in specific applications where you need the axle pressurized a few lsi to seal it and you needed a funky vent, but not applicable to our application here. Im talking some aircraft ground equipment tug axles needef it.

Fwiw my fj80 rear axle on my Tacoma blows out seals and seeps out the fill plug even with the vent running up to the gas door, no cap on the line and the union fitting verified clear, so I have no idea wtf is going on.
 
gt1guy said:
The bellows sure sounds like a great simple solution. It also sounds like you have to get the math perfect or just get lucky. I know I'm not lucky and the math part would just be making up numbers. Plus, I've got ARB's and a leak would make the bellows the same as a plug and goodby seals.

If running a hose up high and still getting oil, would it make sense to increase the size of the hose?
I wouldn't think people are getting a vent hose completely full of oil, but more like a small slug of oil, air, slug of oil, air. Seems like increasing the size of the hose would help reduce the surface tension of the oil and allow the air to pass it by.





Tighter gears will compress the oil more which creates more heat.

Ford 9" creates more heat than other diffs just due to the design and amount of gear contact. What is it called? Hypoid angle?
Click to expand...
Do you know of anyone not having luck with 9" diffs and bellows?
I wonder if a loose mesh will create more airation? Maybe less heat, at first, but fills with air and that's what causes the bubbling out the breather??
 
Slander said:
This. There are some industrial axles in specific applications where you need the axle pressurized a few lsi to seal it and you needed a funky vent, but not applicable to our application here. Im talking some aircraft ground equipment tug axles needef it.

Fwiw my fj80 rear axle on my Tacoma blows out seals and seeps out the fill plug even with the vent running up to the gas door, no cap on the line and the union fitting verified clear, so I have no idea wtf is going on.
Click to expand...
I'm thinking they use a pressure relief instead of an atmospheric vent like we need.
Bigger hose or even bigger tap into the diff might help you... people have also had luck moving the vent the axle tube as well.
 
Sterlingfire said:
I'm thinking they use a pressure relief instead of an atmospheric vent like we need.
Bigger hose or even bigger tap into the diff might help you... people have also had luck moving the vent the axle tube as well.
Click to expand...
The vent on this axle is on the tube, thinking of moving it higher up on the diff.
 
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