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Leaking Transfer Case

G

GalDemSuga

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Folks
My NP 241C is leaking out of the vent line. Any idea as to where I can find that vent plug/check valve at the end of the line. I'm referring to that little plug that allows hot air out but not the fluid?
 
Not a big expert on that one, but if its mated to an automatic tranny, you may have a bad seal that is letting transmission fluid overfill the transfer case.
Actually I suppose a manual transmission would do the same if the seals went bad.
 
Fordum said:
Not a big expert on that one, but if its mated to an automatic tranny, you may have a bad seal that is letting transmission fluid overfill the transfer case.
Actually I suppose a manual transmission would do the same if the seals went bad.
Click to expand...

i'm not losing any tranny fluid only transfer case fluid. I'm not sure what is causing it to develop such pressure to leak so fast. it's perfoming great in both high and low.
 
Well, there is probably only about two things that would let transfer case fluid come out like that. Either it is getting so hot that it is expanding or boiling out, which I would think you would notice either because of the heat, or because a bearing was frozen up and generating the heat along with some noise.
Or, the second reason is that the transfer case is overfilled. I have seen this on some of my equipment when I went through some deep water and it got in and pushed out the oil. Or, you changed the fluid and put in too much.
If you have not been in deep water, or put in any fluid, then I tend to return to my first post.
I am not all that familiar with that model transfer case, I know 205s better. Also, I do not know if yours is divorced ( not mounted on the back of the transmission, driven by a short shaft) or mounted directly on the back of the transmission.
If it is mounted on the transmission, then you can have a seal failure that lets fluid from the transfer case get into the transmission or transmission fluid get into the transfer case.
The last was what I suspected was happening. It does not take a lot of overfill to cause the fluid to bubble out the vent, so if it were coming from the transmission, you might not notice it being all that low.
Hopefully someone else who is more familar with your type setup will jump in and correct me. I am not that good with the 241.
 
Fordum said:
Well, there is probably only about two things that would let transfer case fluid come out like that. Either it is getting so hot that it is expanding or boiling out, which I would think you would notice either because of the heat, or because a bearing was frozen up and generating the heat along with some noise.
Or, the second reason is that the transfer case is overfilled. I have seen this on some of my equipment when I went through some deep water and it got in and pushed out the oil. Or, you changed the fluid and put in too much.
If you have not been in deep water, or put in any fluid, then I tend to return to my first post.
I am not all that familiar with that model transfer case, I know 205s better. Also, I do not know if yours is divorced ( not mounted on the back of the transmission, driven by a short shaft) or mounted directly on the back of the transmission.
If it is mounted on the transmission, then you can have a seal failure that lets fluid from the transfer case get into the transmission or transmission fluid get into the transfer case.
The last was what I suspected was happening. It does not take a lot of overfill to cause the fluid to bubble out the vent, so if it were coming from the transmission, you might not notice it being all that low.
Hopefully someone else who is more familar with your type setup will jump in and correct me. I am not that good with the 241.
Click to expand...

i drove 800 miles from atlanta, ga to clarion, pa and lost about 2pints from transfer case while the transfluid remained unchanged. i have a transcooler hooked up and a deeper trans pan. i will not add any fluid for the next few days and i will monitor my tranny fluid levels.

it just doesnt add up. I put a PCV valve in the TC vent line as i couldnt find a check valve anywhere, so we'll see what happens.

I've also notice that the fluid loss occurs at highway speeds and not during idle. I'm starting to believe that its the input seal on TC and output seal on trans.

Where can I pick up the required seals? What are the part #s?
 
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<I'm starting to believe that its the input seal on TC and output seal on trans.>
Yep, Thats what I think too. I am worried about the pcv valve setup though. That vent has to let pressure out when the oil heats up and air back in when it cools. If the valve does not let pressure out, it will find a way. Probably either through the output shaft seals, or worse yet, back into the transmission. If you are running different fluids in the trans and tranny, that could be bad news for the trans.
As for the seals, they should be standard ones for the two units. Parts houses should have them, but I am sure someone here has a better place to order them. And might even have a part number.

Hello....anyone else want to help here? I'm getting out of my depth......<crickets....><G>

J.
 
Fordum said:
<I'm starting to believe that its the input seal on TC and output seal on trans.>
Yep, Thats what I think too. I am worried about the pcv valve setup though. That vent has to let pressure out when the oil heats up and air back in when it cools. If the valve does not let pressure out, it will find a way. Probably either through the output shaft seals, or worse yet, back into the transmission. If you are running different fluids in the trans and tranny, that could be bad news for the trans.
As for the seals, they should be standard ones for the two units. Parts houses should have them, but I am sure someone here has a better place to order them. And might even have a part number.

Hello....anyone else want to help here? I'm getting out of my depth......<crickets....><G>

J.
Click to expand...

I believe the issue is indeed the Tranny and TC seals. I didnt put fluid in tranny over the last week and it's now about 2 pints low.

I head back to Atlanta on Friday, so I have my work cut out for me.
 
Yep, sounds like you nailed it. Atlanta is a little closer to me than most of these folks, but I don't have any trips scheduled that way in the near future, and its about a 6 hour drive so I won't able to give you a hand.
My last trip up there was back in Sept. when I wired up the telemetry on the Shepard Center's 5th floor.
Unfortunately I did too good a job, and the last report I got was that the system was doing fine.
So I have no reason to go back.
Anyway, let me know what you find.

J.
 
Update***

Ok. I changed out the TC on Monday. It took me all day! I had a backup from my wrecked truck. I replaced the input shaft seal and the trans adapter O-ring and reinstalled the TC.

I then test drove the truck and guess what? Yep, the same leak out of the TC vent hose which I routed all the way under the hood for easy view and access. I then turned my attention to the Transcooler. I figured that maybe it was not flowing freely and I therefore disconnected it. Now the lines are back into the radiator.

I had planned to do some more testing but I was called back to Pittsburgh. After driving 600 miles I noticed the leak was still happening. I'm losing about a pint of tranny fluid every 1000 miles.

I have a deeper pan installed and I'm now wondering if its contributing to the pressure build up. The seals are new in the TC and both the TC and Tranny shift and perform great.

I'm just plain :mad: now. All that hard work and nothing has been solved.
 
Well, I hate to say you have nailed it again, since I was wrong the first time. But at least this one will be easy to check. When the transfer case is reasonably cool, take out the top fill plug. If its over filled, then you have the "Vampire" problem. Transfer cases can't make fluid.
I can't tell from your post, but I think you misread the article. If I am wrong, I apologize.
The problem that the article deals with, is not overheating, it is literally transmission fluid being pumped into the transfer case through a crack in a line inside the transfer case.
It seems that in their infinite wisdom, GM decided it would be a great idea to run the transmission fluid through a line inside the transfer case. When this cracks, it pumps the fluid into the case and out the vent.
From what the article says, the quick fix is to take the input and output lines off the transfer case, and rig up a way to hook them together. Would not hurt to plug the lines coming out of the transfer case too.
Otherwise, it looks like you have a very good chance of burning up your transmission from low fluid.
Actually, an even quicker fix would to be to run the vent tube from the transfer case back into the transmission fill tube.
According to the article, both use the same fluid. This is not a perfect fix, because the transfer case will be running overfull. But its better short term than running the tranny low.
I guess this pretty much has to be the problem. We know transmission fluid is going from the transmission into the transfer case, and you have pretty much eliminated the seals.
I'm not really all that certain if the lines ever need to be hooked back up. From what they say, they did not do a good job of cooling the transfer case anyway, and I'm not sure how much warmup dextron III needs on cold mornings anyway.
Surely someone here has tried doing away with that loop before now.

J.
 
:wink1:
Fordum said:
Well, I hate to say you have nailed it again, since I was wrong the first time. But at least this one will be easy to check. When the transfer case is reasonably cool, take out the top fill plug. If its over filled, then you have the "Vampire" problem. Transfer cases can't make fluid.
I can't tell from your post, but I think you misread the article. If I am wrong, I apologize.
The problem that the article deals with, is not overheating, it is literally transmission fluid being pumped into the transfer case through a crack in a line inside the transfer case.
It seems that in their infinite wisdom, GM decided it would be a great idea to run the transmission fluid through a line inside the transfer case. When this cracks, it pumps the fluid into the case and out the vent.
From what the article says, the quick fix is to take the input and output lines off the transfer case, and rig up a way to hook them together. Would not hurt to plug the lines coming out of the transfer case too.
Otherwise, it looks like you have a very good chance of burning up your transmission from low fluid.
Actually, an even quicker fix would to be to run the vent tube from the transfer case back into the transmission fill tube.
According to the article, both use the same fluid. This is not a perfect fix, because the transfer case will be running overfull. But its better short term than running the tranny low.
I guess this pretty much has to be the problem. We know transmission fluid is going from the transmission into the transfer case, and you have pretty much eliminated the seals.
I'm not really all that certain if the lines ever need to be hooked back up. From what they say, they did not do a good job of cooling the transfer case anyway, and I'm not sure how much warmup dextron III needs on cold mornings anyway.
Surely someone here has tried doing away with that loop before now.

J.
Click to expand...

J
I understand the article clearly. You see my Trans and TC aren't connected as it relates to the ATF flowing through the TC. I've got a 700R4 and NP241C which is stock in my 1989 Blazer. The only way for the ATF to connect is by high pressure forcing it from the Trans (hotter high pressure fluid) pass the input shaft seals and into the TC.
Thats why I made the comparison. Nothing else can explain it.

I'm always driving above 65 MPH for 100's of miles, to and from my work area. This truck came with a rebuilt Trans and a very small Transcooler. It has got roughly 10000-15000 miles on it. I got this truck to replace my wrecked truck and had never driven it before Jan 3, 2010.

I never had this problem with my original truck and it had over 200000 miles on both the engine and trans. That tranny is currently sitting in my garage as a backup.

What I need a better way to cool this tranny. I dont know who built it and what the setup is. If its got a shift kit etc, I have no idea. It does shift like a Cadillac:D. I need a transcooler much like my stock oil cooler and maybe with an electric fan attached. This might help solve my issue but now I've got to wait atleast 3 weeks before I can return home to work on it. Also, is there a vent opening on the Trans? I've never noticed one.
 
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Well, FART!
Just when this thing starts making sense, it all goes screwy again. We have got to be missing something here. You should be able to get that transmission so hot it boils the fluid without it forcing its way into the transfer case.
I cautiously suspect you may have hit on the problem. Any piece of equipment like that has to have a vent of some kind or some way to control pressure.
Under normal operating circumstances its going to heat up and build a few pounds of pressure. Those seal were not designed to handle that. Does the dipstick have a seal on it?
Most of the time I have overheated a tranny, it boiled out the dipstick. But most transmissions lately have seals to keep out the dirt, and they don't let the pressure out.
I know that transmission has some kind of a vent, because this outfit http://www.transmissionhead.com/
sells a tube for it.

I just realized something. I run almost exclusively to Fords, Jeeps, and Mercedes, but it just so happens I have a transmission like yours sitting in a wheelbarrow in my tractor barn.
It came out of a friend's truck we are going to rebuild. I'm going to post this, and when I get a minute, I'll walk out and see if I can find a vent on it.
I'm under the gun right now, I have to head to the swamp shortly, and I need to have a lot of stuff done before I go. But I will post back before I do.

J.
 
Fordum said:
Well, FART!
Just when this thing starts making sense, it all goes screwy again. We have got to be missing something here. You should be able to get that transmission so hot it boils the fluid without it forcing its way into the transfer case.
I cautiously suspect you may have hit on the problem. Any piece of equipment like that has to have a vent of some kind or some way to control pressure.
Under normal operating circumstances its going to heat up and build a few pounds of pressure. Those seal were not designed to handle that. Does the dipstick have a seal on it?
Most of the time I have overheated a tranny, it boiled out the dipstick. But most transmissions lately have seals to keep out the dirt, and they don't let the pressure out.
I know that transmission has some kind of a vent, because this outfit http://www.transmissionhead.com/
sells a tube for it.

I just realized something. I run almost exclusively to Fords, Jeeps, and Mercedes, but it just so happens I have a transmission like yours sitting in a wheelbarrow in my tractor barn.
It came out of a friend's truck we are going to rebuild. I'm going to post this, and when I get a minute, I'll walk out and see if I can find a vent on it.
I'm under the gun right now, I have to head to the swamp shortly, and I need to have a lot of stuff done before I go. But I will post back before I do.

J.
Click to expand...

J
I know where the tranny vent is located now. I'm unable to check for blockage as it is cold as heck outside. However, I will remove the dipstick completely and cover the dipstick tube with a small self breather from the parts store. Kinda like a crack case breather and see what happens.
 
Well, that ought to darn well fix any pressure problems. <G>

The tranny in my barn has a small plastic line coming out of the top of it just right of center, about an inch or so back from the inside back of the bell housing. If that makes any sense. This one was covered in mud, and was facing backwards. When I pulled it up out of the mud and tried to let it go straight, it kinked.
So yours could easily be stopped up with mud, or could have gotten against something and be kinked.
I'm headed for the swamp. The big river is on 21 feet at B'Town, and that will put it over my camp by tomorrow or the next day. So, I am going to have to pull my stuff out quick.

J.
 
Fordum said:
Well, that ought to darn well fix any pressure problems. <G>

The tranny in my barn has a small plastic line coming out of the top of it just right of center, about an inch or so back from the inside back of the bell housing. If that makes any sense. This one was covered in mud, and was facing backwards. When I pulled it up out of the mud and tried to let it go straight, it kinked.
So yours could easily be stopped up with mud, or could have gotten against something and be kinked.
I'm headed for the swamp. The big river is on 21 feet at B'Town, and that will put it over my camp by tomorrow or the next day. So, I am going to have to pull my stuff out quick.

J.
Click to expand...

Good luck and be safe.
 
Well, that was a bust. One of my friends pulled his big camper trailer out tonight so as to beat the water over the road. I told him that tomorrow would be fine, but he was worried. He hauled it to my farm which is where he keeps it during the summer and the first part of the hunting season while we hunt locally.
Had most of my stuff packed up, and was trying to find a station on the satellite that did not have that darned Haiti telethon on, when my Cell phone went off.
Seems my friend was trying to circle around so he could park the trailer facing in the right direction, when the bottom fell out and he bogged up to about the doors.
So, I headed back home.
Got here about 11:00. grabbed some planks and plywood and we built a walkway from the door of his pickup truck where he was sleeping waiting for me, to the front door of the trailer.
He climbed in and went to bed. I came into the house and am going to be myself. In the morning, when we can see, we will see how to get him out.
I think the best way is to dig down and put a platform under the tounge jack and unhook the trailer. Then I can winch his truck out and leave the trailer there.
Its fine where it is, he is not going to use if for a few weeks. After the ground dries out some, I will go out there and shovel some dirt under and in front of the tires. Then back my truck up and tow the trailer out.
The winch on the front of my truck would have no problem pulling them both out, but as the trailer goes deeper and deeper, it is going to start dragging off the jacks, and maybe damage the septic tank or lines.
Once the ground dries out enough, I can roll it out.

J.
 
For anyone following this thread and wondering, I got him out just after daylight. I went over and picked him up about 5 and we went for coffee.
Then, when it got light enough to see, we put a 4X6 under the tongue jack and disconnected the trailer.
I then drove my truck as close as I could and stay on solid ground, and bogged over to his truck with the cable.
I was a little worried, because while I have about 180 feet on my winch, it was a long way to his truck.
Turns out, I wound up with one layer on the spool.
I only had to pull him about 15 feet, when he hit the hard ground he was supposed to be on last night.
This left me with a LOT of cable spooled out, and needing to get back down to the camp before the water got too high.

So, I ran the cable up over the hood, across the right side mirror, wiring it to the mirror mount, and coiled it up in the back of the truck.

This hydraulic winch is scary strong, but its slow to wind in. Especially when you are trying to do it under tension and laying the wraps straight.

I made a mistake when I ordered this winch.
I got it with the single speed. 8ci motor. The offered it with a 5/10ci two speed motor.
It would have meant a little more plumbing, but then I would have had a winch that pulled harder per PSI, which would have meant less strain on hoses and pump, but that could be shifted to high speed to reel in the cable.
By the time I found out, I had already mounted the winch, and there was not enough room for the other motor which is about 2 inches longer.

Anyway, I got all the important stuff out of the swamp and got my trailer moved to higher ground, since the water was too deep to drag it out without getting the floor wet.
Driving out, down the main national forest road, I spooked a big fish, probably a carp or catfish swimming down the road in front of my truck.

Tomorrow, I will pull the cable out to the even part, hook it to a tree, lock the emergency brake, and let the winch slide the truck up to the tree while I guide the cable back on properly.
I will just let the truck idle so I have plenty of time to get it right.

You know, not being quite as young and foolish as I used to be, I might get a friend of mine to come and sit in the cab ready to turn off the engine just in case.
I love PTO winches, but even at idle, mine has more than enough power to wind my fat ass up in it if I got hung in the cable.

J.
 
I'd get some help J. Sounds abit dangerous doing it alone.

I'm still being run ragged by this Trans issue. I've checked the Trans vent hose for clogs and didnt find one. I removed the dipstick and then drove her and still continue to lose fluid via the TC vent hose.

It continues to spill fluid into the TC. I inspected the fluid in the Trans and it's redish still but I'm worried now. I removed the top line @ the Radiator to ensure that there was flow and there was. I need to find out how hot the fluid is coming from the Trans.
 
GalDemSuga said:
I'd get some help J. Sounds abit dangerous doing it alone.

I'm still being run ragged by this Trans issue. I've checked the Trans vent hose for clogs and didnt find one. I removed the dipstick and then drove her and still continue to lose fluid via the TC vent hose.

It continues to spill fluid into the TC. I inspected the fluid in the Trans and it's redish still but I'm worried now. I removed the top line @ the Radiator to ensure that there was flow and there was. I need to find out how hot the fluid is coming from the Trans.
Click to expand...
Did you ever get your TC leak fixed? I have a 1990 GMC 3/4 suburban with the same issue. Pukes fluid out of the vent tube if I go over 45mph.
 
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