How to vent a axle housing via a 1/4 pipe opening, or should I?

peter · Jul 16, 2014

I know this is way OT, But; the expertise on this forum is such I am sure I can get ideas.

I have a Kubota 4wd tractor with a slight leak at the front axle, where the wheels pivot when steering. There is some school of though that the lack of an axle vent aggravates this leaking, which apparently is common on Kubota. Or atleast common as the seals wear. These leave the factory with hydro oil. That usually get replaced with gear oil after some specified service interval. I just today replaced the fluid (1000 hrs and 12 years later). Seals maybe next. I understand, sometimes gear oil is enough to reduce or eliminate the leak.

I though a small breather might be good insurance. Certainly if I do the seals, like it to be the last time.

Any opinions on this idea? Heat and expansion, contributing to fluid leaking out from a sealed axle unit?

I can easily drill and tap 1/4 pipe into the filler cap. Is there a cheap simple breather off the shelf that just screw on? Maybe a gitts flip up oil cup filled with steel wool?

Or is this a lot of fuss about nothing?

johnoder · Jul 16, 2014

Been a long time (mid nineties) but I think the dark spot on this nine inch Ford I narrowed is the vent, though not a NPT style

http://img.photobucket.com/albums/v337/johnoder/Ford9/01.jpg

SteveBausch · Jul 16, 2014

I recall vents on automotive drive axles..

And "drive axle vent" pulls up a $3 unit:
Jeep Part jep68017179aa - Axle Vent - Fits 2007 to 2015 Wrangler, Rubicon and Unlimited - 4 Wheel Parts

Makers pull bone-headed moves like this all the time. Honda's VFR 750 has the ignition wiring running alongside the primary wiring, and guess what? The owners can't keep voltage regulators in them

The Extractor · Jul 16, 2014

Vent it as when it warms up it creates pressure and makes leaks.

Limy Sami · Jul 16, 2014

Vent it, and it's probably quicker to modify the filler plug and run a bit of plastic tube up out the way, than faff about trying to find a part.

FWIW If those JEEP vents are the loose ball type like the Land Rover - they soon bung up with mud etc .

swatkins · Jul 16, 2014

I remember a vent on one of my older Chevy pickups. They also ran a rubber hose, from where the vent was tapped, up as high as they could place it under the bed of the truck to kept the opening out of high water.

SpongeRich · Jul 16, 2014

Rather than venting it to the open air, you might try fitting a little bellows that'll allow expansion without letting in any contaminants.
I used on on one of my ATV's.... it's an EZ-Go golf cart part. Think I paid about $10 for it.

Patrick H · Jul 16, 2014

I wouldn't bother venting it. Just making a place for water to get in the housing. Those seals usually start leaking from running in 4wd while carrying weight (usually too much) in the loader. Running in 4wd on hard surfaces really accelerates it. I use to maintain and repair a fleet of Kubota equipment and replacing those seals is about a 30 minute job per side. Just make sure you have some good snap ring pliers. I always ran hydraulic fluid in the front. This was in late '90s L series of multiple models. Also, try to keep the dirt washed out of that joint as much as possible. It really does add to the life of the seals.

peter · Jul 16, 2014

Sounds unanimous - some vent is a good idea. I like the idea of rubber line up under the hood. I just went ahead and tapped a hole in the filler for 1/8 pipe (not 1/4 afterall). Stuffed steel wool into a spring top Gitts machine oiler. Got the oiler attached at the end of a scrap of fuel line. Now just find a fitting for other end.

Done

peter · Jul 16, 2014

Oh, oh... Just read Patricks input. Well.... Worse case, I can plug that hole. Time for a break.

And the dirt. I did see a lot crap jammed up in there. Cleaned that all out this am, just so; I could watch for leaking.

I rarely use the 4WD, but I am 2nd owner. The first guy got the best 1000 hours and apparently did not believe in following any scheduled service.

DrHook · Jul 16, 2014

nice work on the nine, Johnoder!
I've done a lot of housings for drag cars and put vents on all the ones that do NOT leak.

if you will be driving in water as deep as the housing, use a barbed fitting, a piece of hose and an in line fuel filter to keep out the dirt. Otherwise, any hardware store has the sintered bronze type plugs that work fine.

johnoder · Jul 16, 2014

Thanks for kind comments.

DrHook said:
nice work on the nine, Johnoder!
I've done a lot of housings for drag cars and put vents on all the ones that do NOT leak.
if you will be driving in water as deep as the housing, use a barbed fitting, a piece of hose and an in line fuel filter to keep out the dirt. Otherwise, any hardware store has the sintered bronze type plugs that work fine.

t.jones · Jul 16, 2014

You only need to vent something if it's getting hot enough to expand the air contained signifigantly . A little bit of expansion may cause pressure so the seals work better. If you vent to the outside air you will collect moisture and the gears probably don't run hot enough to " burn " it off. ---Trevor

Limy Sami · Jul 17, 2014

t.jones said:
You only need to vent something if it's getting hot enough to expand the air contained signifigantly . A little bit of expansion may cause pressure so the seals work better. If you vent to the outside air you will collect moisture and the gears probably don't run hot enough to " burn " it off. ---Trevor

I've replaced enough axle oil seals and brake parts to shoot that theory down 10,000 time over.

michiganbuck · Jul 17, 2014

What were they thinking?… That the dipstick line or check level hole is low enough to allow air space to give enough heat expansion to hold a little pressure. Not saying they were 100% right. Perhaps replacing the seal is the way to go… then never over fill. Drill and tap or just drilling to make vent could make chips in the works with not taking it apart and with taking it apart you should replace the seal. *As someone said (Limy) the vent filler plug could be vented with not putting chips in the works.
Kubota Tractor Front Axle Bearing Repair Part 1 - YouTube

baldwin · Jul 17, 2014

I fitted a commercial breathing filler cap to the gearbox I have just built for an IC engined model loco. The filler has what amounts to a spring loaded rivet which seats on an O ring. The cap can burp, but cannot suck air back in. I thought it would help me avoid the sort of trouble you are having.

Steve

Andy FitzGibbon · Jul 18, 2014

baldwin said:
I fitted a commercial breathing filler cap to the gearbox I have just built for an IC engined model loco. The filler has what amounts to a spring loaded rivet which seats on an O ring. The cap can burp, but cannot suck air back in. I thought it would help me avoid the sort of trouble you are having.

Steve

I would look for something like this, rather than an "always open" vent. Or, just plug it, and live with occasionally replacing a seal. Since the front axle is an intermittent-use item, moisture from outside air will likely collect in the fluid and won't be "burned" off by fluid heating and circulation. Hydraulic oil seems to be pretty hygroscopic, which doesn't help matters. I would guess that Kubota didn't put a vent on the front axle for those reasons. Once water gets into the fluid and gearbox, it's pretty hard to get it out. A friend of mine is going through this right now with the combined transmission/hydraulic reservoir on his tractor. He's flushed it out several times, but there's still water in the fluid, and the use that he gives it doesn't often heat the fluid enough to "burn" the water out.

As I recall, my Kubota (L3430) doesn't have a breather on the front axle, either.

Andy

jim rozen · Jul 18, 2014

I think mcmaster carr still sells the NPT pipe plugs that have a porous sintered bronze
plug in them. That's what I'd use.

clay27bsouthbend · Jul 19, 2014

On a non-vented housing it would draw in moisture anyway past a seal. Check out the four wheeler web sites. I'm sure they have some good ideas that will work for you. My 1980 Jeep had rubber hose running up along side the radiator.

peter · Jul 19, 2014

Not sure I mentioned this. I removed the filler plug and drilled and taped for 1/8 pipe. So- no metal chips in the front end. I ran a hose up under the hood with a filter on the end. I will look at the fluid next year. I would rather drain and refill occasionally than have a leaky mess on the floor or chronic seal replacement issue. That is assuming the worse. Of course if the answer was clear I would follow that convention. Seems like opinions vary, so; time will tell. One thing for sure, Kubota has a real problem wearing seals on the front axles. As costly and popular as Kubota is, I still feel this tractor is built to a lower end price point. There are quite a few short cuts. It is fine and overkill for what I use it for, just saying Kubota is far from my gold standard of tractor design.

And BTW, I replace the hydro fluid with heavy wt gear oil in the front axle. Two birds with one stone. Higher viscosity hopefully slow the leak and unknown fringe benefit should be more moisture tolerance. The dealer told me they swap out the hydro fluid with 80-90 gear oil on all the Kubotas that come back in for periodic service. Gear oil is SOP for Kubota.

I used the tractor a few days ago. I just took a minute to check out in the garage. Not one drop on the floor. Prior to fluid swap and vent there would be a nice little puddle starting to form. Not saying it was the vent. Not saying that at all. I also swapped out the fluid for gear oil. Next year will tell the story on moisture.

How to vent a axle housing via a 1/4 pipe opening, or should I?

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