NP241 venting fluid fix?

[dyeager535]

I'd really rather not revisit the fluid capacity debate on the 241, but I need to do a couple of things to it anyway, so if possible, I'd like to resolve the venting fluid issue while I'm in it. I already have a "fix" that works, but it's external and it adds a bunch of junk and places to leak. Plus makes checking fluid difficult. And if it's difficult, I'm less prone to keeping up on it.

GM/NP knew there was an issue, as evidenced by the early/late case castings (apparently this change happened when they went to IFS so I/you can't just get an updated case):

I have to drill and tap the vent since it's no longer a snug press fit anyway, any ideas on how to shield the vent from the fluid that gets thrown on it?

It looks like there is enough meat there on the inside to tap a hole for a 4-40 or 6-32 screw. Maybe bend up a metal deflector and use the screw to retain it? A "U" shape perhaps?

Somewhat on topic, does anyone know why the vents are so large on any of the components? In this component, it doesn't seem like there would ever be a large/rapid enough temperature change to necessitate such a large opening. I've seen people tap it and use a 1/8" fitting, I'm assuming they don't have issues with fluid being pushed past the seals.

 

[diesel4me]

If your going to tap it for 1/8" NPT,maybe you could put one of these brass barb fittings with a sintered bronze filter on the other end of a hose routed up far enough to discourage the fluid from being pumped out ?..


Only other thing I could think of it to make a "catch can" for the fluid to collect in that is vented,at least then you could catch the fluid instead of it leaking and making a mess..

 

[dyeager535]

If your going to tap it for 1/8" NPT,maybe you could put one of these brass barb fittings with a sintered bronze filter on the other end of a hose routed up far enough to discourage the fluid from being pumped out ?..Only other thing I could think of it to make a "catch can" for the fluid to collect in that is vented,at least then you could catch the fluid instead of it leaking and making a mess..

The problem is that the fluid is actively pumped into the vent at higher speeds, so no length of hose will fix it...I'm trying to tread carefully so as not to get into the fluid capacity issue, but if people use the 2.7pt(? Think that's the one number you see) fill, which is not to the bottom of the fill plug, typically they don't have an issue venting. If you go to the fill plug, it's more like 2.7qts. you'd need a catch can capable of holding about a quart and a half.

FWIW, I do have a sintered bronze filter on the vent line that is run up to my firewall for the t-case though, that was my first attempt at a fix, before I knew what the actual problem is.

This is an interesting topic, regardless. Not everyone says they have an issue, even though all the cases are the same. It often shows up after changing components in the drivetrain which lead to higher freeway RPMs...but even miniscule changes in RPM have triggered it for some, and in my truck, my RPMs are generally pretty low...no OD, but 3.42s/33's. And who knows? Maybe people who say they don't have an issue don't pay attention and haven't noticed they vented half their fluid.

 

[Wes Harden]

How about a different location?
I haven't been inside a 241 so not sure if there is a better, or possible relocation spot.
Pipe plug the old add new

 

[dyeager535]

How about a different location?
I haven't been inside a 241 so not sure if there is a better, or possible relocation spot.
Pipe plug the old add new

That's not a bad idea. Would be simple thats for sure. Wonder if the case is thick enough to support an NPT fitting elsewhere.

Hell, that gives me an idea. No real reason it couldn't be vented through the fill plug. That wouldn't be a pain to deal with even when checking the fluid level, as long as it was just a hose/nipple. I imagine for the odd time the nose COULD be up enough to shift the fluid back that high, a long hose would keep it from puking since it would no longer be under pressure.

 

[Wes Harden]

Only thing I see that might be an issue with fill plug, is fluid expansion from heat. Level could rise up beyond plug.

 

[TreeFarm]

maybe tap the tail housing for a vent. less moving parts in that area. You could always have a bung welded on if its too thin to tap.

 

[6872xtc]

Moving the vent sounds intriguing. What about adding 2nd vent and tying the two together with a tee?

I am surprised that yours doesn't have the deflector, the two 1990 ones that I have had part for mine had it, I believe.

I put a clear plastic fuel filter in the vent hose for my rear differential. I tried to keep it pointed up, but not completely vertical, to try and give a place for the oil to drop out of the air stream. I believe that the idea of the larger diameter hose and opening is have more space for the oil to get out of the air stream. Lower velocity.

 

[dyeager535]

Moving the vent sounds intriguing. What about adding 2nd vent and tying the two together with a tee?

I am surprised that yours doesn't have the deflector, the two 1990 ones that I have had part for mine had it, I believe.

I put a clear plastic fuel filter in the vent hose for my rear differential. I tried to keep it pointed up, but not completely vertical, to try and give a place for the oil to drop out of the air stream. I believe that the idea of the larger diameter hose and opening is have more space for the oil to get out of the air stream. Lower velocity.

I can't find the pic I took, but I actually already run a "three way vent setup", but it's just too much junk there. The original vent exits the case, I have the hose going downward, where I have a tee. One leg goes off to the firewall, and it's pointed upward to discourage fluid migration. The second leg continues down, and goes in through a bushing/fitting I have installed in place of the fill plug.

It works fine as far as I can tell (only leaks from the adapter and I think that's a separate issue) from the couple years it's been there, and I only used spring clamps.

But maybe as suggested, plug the factory vent line, use the fill plug as the vent, and use a clear fuel filter secured horizontally to at least give the fluid a chance to separate. I kind of suspect it would in the ~10ft or so of hose, maybe try without first. Vent location will make it real clear if its not working as I hope.

Not a bad idea to account for expansion, even at 2.5qts I don't think there would be much? But expansion + uphill maybe a bit of an issue. It seems no issues running at 2.7pts, apparently fluid level isn't real critical, so it wouldn't be terrible to fill to less than the plug.

 

[87blazerK5]

I can't find the pic I took, but I actually already run a "three way vent setup", but it's just too much junk there. The original vent exits the case, I have the hose going downward, where I have a tee. One leg goes off to the firewall, and it's pointed upward to discourage fluid migration. The second leg continues down, and goes in through a bushing/fitting I have installed in place of the fill plug.

It works fine as far as I can tell (only leaks from the adapter and I think that's a separate issue) from the couple years it's been there, and I only used spring clamps.

But maybe as suggested, plug the factory vent line, use the fill plug as the vent, and use a clear fuel filter secured horizontally to at least give the fluid a chance to separate. I kind of suspect it would in the ~10ft or so of hose, maybe try without first. Vent location will make it real clear if its not working as I hope.

Not a bad idea to account for expansion, even at 2.5qts I don't think there would be much? But expansion + uphill maybe a bit of an issue. It seems no issues running at 2.7pts, apparently fluid level isn't real critical, so it wouldn't be terrible to fill to less than the plug.

Sorry to bring an old post back, but i have been struggling with this issue for a while, and am just wondering if you ever came up with a final fix? If not, I am going to try to use the tee method you mention here. I've read everything the internets has to say about this topic and your solution makes the most sense to me. It may be more parts, but it should at least be self contained this way.

 

[dyeager535]

Sorry to bring an old post back, but i have been struggling with this issue for a while, and am just wondering if you ever came up with a final fix? If not, I am going to try to use the tee method you mention here. I've read everything the internets has to say about this topic and your solution makes the most sense to me. It may be more parts, but it should at least be self contained this way.

I do have somewhat of a pic to show it...

Hose comes out of the vent, loops back so fluid is theoretically "falling" down towards the tee, and hopefully deciding to go straight down via gravity, past the actual vent line that goes to the firewall. I've had zero issues with this setup actually, I've had no time to change it, but that's what happens when something works. Lol

I suspect it could be done a lot more cleanly and cheaply with plastic quick connect fittings and plastic lines.