Venting the front axle on CUTs(with pics)

[Rob-D]

Did you look at the pictures in the thread I started?


Oh that is precisely what I'm going to do if I ever have to drain it to replace any seals or bearings!

Me too! I was thinking the same thing. If this box ever comes apart I'm drilling a hole in it!

I didn't see the pics I'll go back and look.

Rob

 

[The Haymaker]

Maybe I missed it, but I don't see anyone mentioning the fact that those vents on the trannies and x's of vehicles are usually relocated by anyone planning on doing more than driving down improved ways. I see the same issue with a low vent as many bearings and seals. You warm them up in operation, then hit water and they rapidly cool, creating a suction.

Personally, I think if all is up to spec, don't think the volume of a CUT front end is great enough to become that big of a problem.

I'll leave mine airtight, therefore, water tight.

Nice, creative method for installing that vent though. Very sano. I like!

 

[Rob-D]

Arrabil,
I couldn't findthe exact post you talked about how the problem occured after months of good service but I gathered from other posts that you were parked on a hill in 104 F and the vent filled with oil.

OK, two conditions have to be met for this to happen.

1. There must be pressure in the case
2. Oil must be up too the vent hole.

You start mowing on an incline (cool tranny) and the tranny gets hot (pressure builds) but the incline is so great and continuous that oil blocks the vent tube. Out comes the oil. This is my guess how it happened. It fits both criteria and is possible. To prove it you could let the tractor cool and mow the incline in the opposite direction (vent unblocked) to see what happens.

I'd like to say the 'nicest' way to fix it is to have a vent at each end of the tranny or perhaps one in the middle but we can't do that without drilling.

You could run a vent with a tube in it long enough the reach the middle of the tranny. This might work but you would have to pull the case apart to set it up and you might as well drill a hole if you're going to do that!

Your problem shows just how much pressure builds up AND the real possibility of dirt being drawn in as the box cools. Just where we don't want it, at the bearings!

As far as not venting the front box to keep a positive pressure as someone said, I don't believe it, the tranny is vented. If it doesn't need positive pressure why does the front axle?

The easiest solution is the one you raised about a holding tank. I think a large aluminum fuel injection filter (2"x3" or so) would work nicely. Just run a tube to it and you're done. It filters and stores excess without any other a parts. Just mount it vertically.

Rob

 

[Rob-D]

Maybe I missed it, but I don't see anyone mentioning the fact that those vents on the trannies and x's of vehicles are usually relocated by anyone planning on doing more than driving down improved ways. I see the same issue with a low vent as many bearings and seals. You warm them up in operation, then hit water and they rapidly cool, creating a suction.

Personally, I think if all is up to spec, don't think the volume of a CUT front end is great enough to become that big of a problem.

I'll leave mine airtight, therefore, water tight.

Nice, creative method for installing that vent though. Very sano. I like!

The problem with your theory is that water hitting the tranny wouldn't cool it fast enough to create suction. It's not a thin exhaust pipe, it has mass, you can't simply spray it with water and cool it. If you've ever welded you know that you can spraywater on a joint and it takes a long time to cool. The bigger it is the longer it takes, now imagine something the size of a front axle.

The second thing is that there are problems and the "water tight" plug you talk about - isn't. When the tranny gets hot it pushes oil out and when it cools it draws in dirt water or whatever is nearest the seals. A small vent, say 1/16" will allow a stable pressure and allow very little if any water in, that's why trannies are vented. A race car going 150+ mph hits a water puddle, does the tranny suck in water? Hardly. Think of a tranny as breathing, a vent allows that.

Rob

 

[arrabil]

The oil must have been up to the vent hole. But it went up the tube on its own. I didn't start it, run it, mow with it, nothing. I was in the process of cleaning the fuel tank and had been for three days. I noticed the oil on the third day when I was hand priming the fuel pump. It could have been like that for all three days or just three hours; I don't know.

I let the tractor sit for a day after that and the oil never went back down the tube. I then drove it to its normal, flat parking spot, and the oil didn't go back down either. Thats when I drained the excess.

Since the oil doesn't go back down on its own, there is too much capillarity/surface tension as suggested by dfkrug. The oil needs to drain on its own under any temperature/pressure for the overflow box to work. So that seems to be shot too.

You see any holes in that?

 

[The Haymaker]

The problem with your theory is that water hitting the tranny wouldn't cool it fast enough to create suction. It's not a thin exhaust pipe, it has mass, you can't simply spray it with water and cool it. If you've ever welded you know that you can spraywater on a joint and it takes a long time to cool. The bigger it is the longer it takes, now imagine something the size of a front axle.

Huge difference between splash hitting and true submersion, which seems to be what the topic is. I've found that by the time I have my front axle submersed, then chances are it's gonna be there long enough for me to either pull myself out with the bucket, grab the come-along, or go buy another 12 pack for whichever neighbor is volunteered to rescue me. An axle immersed in water is not going to take long to cool, and it won't take long to create suction. I'd rather have the water and debris have to work around a seal than straight through a vent.

The second thing is that there are problems and the "water tight" plug you talk about - isn't. When the tranny gets hot it pushes oil out and when it cools it draws in dirt water or whatever is nearest the seals. A small vent, say 1/16" will allow a stable pressure and allow very little if any water in, that's why trannies are vented. A race car going 150+ mph hits a water puddle, does the tranny suck in water? Hardly. Think of a tranny as breathing, a vent allows that.

Rob

If the plug is not tight, then it's be able to deal with the gradual pressure changes and we wouldn't be talking about venting? Still seems to me that if I can build enough pressure in the limited space of an X to blast seals, then chances are there was a mechanical issue or I had too much oil, therefore not enough air volume. Just like overfilling a crankcase, if there's no air to compress, the pressure WILL find a way out.

Show me a race car that hits water at 150mph that is deep enough to reach a vent (I, again, don't think splash is an issue) and I'll show you a race car with bigger issues than water contamination and a race driver with loin cloth contamination.

You keep mentioning tranny. A tranny would have a FAR broader operating temp. range to deal with than a front end. No comparison.

As for running a vent tube, which would be my option if I felt a vent was warranted, there is no need for an expansion tank. Just run the hose up to a high point, such as the radiator support, loop the end down, and put a small inline fuel filter on it. If you can lift an axle end higher than that point, I hope you have your ROPS up and seatbelt on.

Think simple, less things to break.

 

[kuboman]

I was not suggesting we all go out and drill and tap our axles. What I said was is that the larger farm tractors have a vent prefabbed into the axle. They are vented from the factory.
All my farm tractors (11) are vented, my b1550 is not, my b2620,3200 are. If you want to fabricate a vent into yours I think it would be a good idea. If you don't that is your choice.:thumbsup:

 

[Rob-D]

Huge difference between splash hitting and true submersion, which seems to be what the topic is. I've found that by the time I have my front axle submersed, then chances are it's gonna be there long enough for me to either pull myself out with the bucket, grab the come-along, or go buy another 12 pack for whichever neighbor is volunteered to rescue me. An axle immersed in water is not going to take long to cool, and it won't take long to create suction. I'd rather have the water and debris have to work around a seal than straight through a vent.



If the plug is not tight, then it's be able to deal with the gradual pressure changes and we wouldn't be talking about venting? Still seems to me that if I can build enough pressure in the limited space of an X to blast seals, then chances are there was a mechanical issue or I had too much oil, therefore not enough air volume. Just like overfilling a crankcase, if there's no air to compress, the pressure WILL find a way out.

Show me a race car that hits water at 150mph that is deep enough to reach a vent (I, again, don't think splash is an issue) and I'll show you a race car with bigger issues than water contamination and a race driver with loin cloth contamination.

You keep mentioning tranny. A tranny would have a FAR broader operating temp. range to deal with than a front end. No comparison.

As for running a vent tube, which would be my option if I felt a vent was warranted, there is no need for an expansion tank. Just run the hose up to a high point, such as the radiator support, loop the end down, and put a small inline fuel filter on it. If you can lift an axle end higher than that point, I hope you have your ROPS up and seatbelt on.

Think simple, less things to break.

24 hours of Le Mans has cars racing in the rain. When I worked on 911 Porsches they had the vent on top of the tranny, going as fast as they do water hits everything. We never had problems, not ever.

The filter does exactly that. It filters air or the small amount water entering the box- not dirt. An axle sucking in through a seal has not filtering mechanics.
It's not the temp range it is what is happening in the front end axle or tranny. Either case the last thing you want is pressure building up.

If someone starts with a cold case and mows on an steady incline for a period the front axles will bias the oil to one side or the other. If the oil is biased towards the vent than just a tube won't fix it, oil will push out the tube. It's not how high you lift the axle, the vent is under oil and the air in the case is expanding.

Rob

 

[Rob-D]

The oil must have been up to the vent hole. But it went up the tube on its own. I didn't start it, run it, mow with it, nothing. I was in the process of cleaning the fuel tank and had been for three days. I noticed the oil on the third day when I was hand priming the fuel pump. It could have been like that for all three days or just three hours; I don't know.

I let the tractor sit for a day after that and the oil never went back down the tube. I then drove it to its normal, flat parking spot, and the oil didn't go back down either. Thats when I drained the excess.

Since the oil doesn't go back down on its own, there is too much capillarity/surface tension as suggested by dfkrug. The oil needs to drain on its own under any temperature/pressure for the overflow box to work. So that seems to be shot too.

You see any holes in that?

Well the first thing is capillary action will only work with what is in the tube. So if you keep sucking out the vent than the oil has to be up to it. There has to be continuity, oil can't simply splash on the vent hole there has to be a constant source. The other thing is that capillary action will only take us to the point where the downward force keeps it from going any higher. It seems to me from what you are saying that the vent tube somehow is below the oil line.

An overflow box will work if the case gets hot. let's say there is oil in the tube but the vent is not sitting in oil. When the case gets hot and expands it will push oil and air up the tube into the holding chamber. any 'extra' air will push past the oil in the holding chamber as bubbles. Once the case cools the air contracts and draws only oil back into the tranny.

If your oil didn't go back into the tranny it was because the pressure was equalized. IF the vent is not in the oil the next time the case gets hot it will push air past the oil in the holding chamber and draw it back into the tranny when it cools. The vent must be above the oil line for this to happen, again, I'm not sure yours is from the description you gave.

Rob

 

[chopped]

A simple PVC plug with a hole drilled on the side would do.