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Np241 burning up range hub

My brother has a Jk 241 (non rubicon case) in his JK on junkyard 1 tons and 40s with locking hubs.

He’s done countless 1000+ mile road trips with no issues. My guess is it’s getting fluid somehow. He also has a rubicrawler (241 planetary) in the tailhousing on his 42RLE so it’s essentially the same doubler setup you have.
 
I know there are a few different thickness of collars to engage the planetary. Also some can be put in backwards that puts too much pressure on the thrust washers and builds tons of heat. Had it happen with a my 231 doubler box I got used. Check both thrusts washers to see if one has more wear.
 
06h3 said:
My brother has a Jk 241 (non rubicon case) in his JK on junkyard 1 tons and 40s with locking hubs.

He’s done countless 1000+ mile road trips with no issues. My guess is it’s getting fluid somehow. He also has a rubicrawler (241 planetary) in the tailhousing on his 42RLE so it’s essentially the same doubler setup you have.
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Thanks. I assumed there were people out there. Running this case.. maybe it was my old shifter setup. Just not sure how.

Baldy said:
You guys are overlooking the obvious here. His problem is the shift fork was made in Canada, duh!
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Lol.. dammed after market parts..

Tydes said:
I know there are a few different thickness of collars to engage the planetary. Also some can be put in backwards that puts too much pressure on the thrust washers and builds tons of heat. Had it happen with a my 231 doubler box I got used. Check both thrusts washers to see if one has more wear.
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Yes, I'm aware of that. The jeep Np241 is it's own collar. Learned that the hardway previously. This current case has not been opened. But I'll inspect everything when I split this case open.
 
This morning my Facebook decided to give me this memory from 3 years ago. This is what it looked like when it burnt up but with the main shaft removed.
FB_IMG_1704381401233.jpg
 
I dont think this is solving for the root cause of the problem but I always wondered by NWF or someone hasnt created a bronze pad. Maybe its too stiff?
 
06h3 said:
I dont think this is solving for the root cause of the problem but I always wondered by NWF or someone hasnt created a bronze pad. Maybe its too stiff?
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The hardest part would be getting them to stay on i think. But once again, I think that's trying to solve a non existent problem. It's just me.. i always get the difficult problems...
 
My blackbox burnt up those shift pads
 
Domer said:
The hardest part would be getting them to stay on i think. But once again, I think that's trying to solve a non existent problem. It's just me.. i always get the difficult problems...
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I can relate :shaking: I have stupid issues, maybe its me...lol
Domer said:
When I pull it apart I'll inspect it closely and see if it's wear or just markings.


Well.. that's interesting..
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II have been following Bmxbry9 saga as well. His pads burnt up to due to low fluid. I would say its 2 different issues.
 
Domer said:
When I pull it apart
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Until then, shall we bet on how many pages this thread will be in 2 weeks :flipoff2:

On a serious note- what’s your wheeling/driving style is like? In the first post you said you barely had it in low-low, just in low. Which case you had in low the most of time? And did you do a lot of high speed driving with the 241 in low? With a manual it’s easy to skip up into high gear.
 
TrailTamer said:
Until then, shall we bet on how many pages this thread will be in 2 weeks :flipoff2:

On a serious note- what’s your wheeling/driving style is like? In the first post you said you barely had it in low-low, just in low. Which case you had in low the most of time? And did you do a lot of high speed driving with the 241 in low? With a manual it’s easy to skip up into high gear.
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Lol. Hopefully the discussion continues and have a viable solution by the time I get home.
This time it was freeway driving, 4 high, and some 4 low in the snow. I think I used double low 1 or twice on this case. Haven't really beaten on it at all. I usually don't wind up the rpms in low if I don't have to. I'm assuming the burn is coming from the freeway speeds and either lack of oil or excess pressure on the fork for some reason. That's the only 2 things it can be... I don't think clocking it up would cause any problems. The oil pickup is still submerged, and nothing else has damage. The 4wd fork is always fine, and it has plastic pads. I'm almost betting on a lack of oil flow for some reason.
 
Well, I believe I did it good this time. Have the cases pulled and drained them. Super dark fluid, lots of metal and plastic and found a piece of a thrust washer. I'll get it torn down tonight and see how much is broken.

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Oof man. Such ad odd issue considering how many combinations it has chased you through. That thrust washer chunk reminds me of the ones between the planetary input and the "cage". But why...
 
fl0w3n said:
Shift linkage? What if the linkage to the main case is keeping tension on the shift collar

That would explain why it spins smoothly on the bench, because linkage isn’t binding yet until you get it in the vehicle

Edit - I see you’ve ran mechanical and cable, but I’d still look into it. If you can’t replicate drag on the bench, it’s gotta be something associated with the final instal conditions
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Skinny said:
I think if you had that much slop in the shafts and planetaries it would have trouble shifting, staying in gear, etc. also be extremely noisy.

The operating principle of that case has been used on hubs, no hubs, and vacuum disconnected axles. I wouldn't sweat that.

There are also a lot of JK on up guys running Ford axles with hubs and these are not melting down left and right.

If the unit was getting that hot you would have discoloration on a lot of other components.

I hate to say it, my gut is the shift mechanism is holding pressure on it somehow and smoking the pads and fork from not being centered at rest.
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I agree. Some how the linkage is off. This a unique failure to this Jeep. It's not inherently an issue with the 241.
 
AgitatedPancake said:
Oof man. Such ad odd issue considering how many combinations it has chased you through. That thrust washer chunk reminds me of the ones between the planetary input and the "cage". But why...
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That's definitely what this will be. I'm getting another case from the junkyard most likely.

TRINDU said:
I agree. Some how the linkage is off. This a unique failure to this Jeep. It's not inherently an issue with the 241.
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I have a completely different shifter setup now. Running a JBfab cable shifter. (Also this is a doubler in my Dakota.. just a jeep case.. lol) and I also believe it's not a 241 issue as I can't find any other issues on the web resembling mine. Just need to figure out what exactly is causing it.
 
That's odd wearing range forks like that. The chunk of planetary output gear thrust washer seems to point at the fork holding pressure on the planetary . There's got to be something wrong with the detent positions or a missing snap ring on the planetary. The 241 output flange snap ring would be damaged if the doubler was pushing on the input shaft so you can rule out the doubler.
 
Well, got the case tore down. Somebody has been in it. There is black rtv all over. And the broken thrust bearing is completely gone.
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Since that is the most likely culprit since everything can move now.. I went ahead and pulled out my old case as it's still under the bench and pulled the planetary.. guess what.. it's missing a thrust washer.. I'm a fucking retard... pretty sure I forgot it.. it was probably missing the first time it burnt up, and I never put one in..
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06h3 said:
May as well throw the bronze ones in for some extra strength. They won’t break down like the plastic ones do
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Id love too.. but at $200 per case right now.. that's kind of spendy...
 
Domer said:
Id love too.. but at $200 per case right now.. that's kind of spendy...
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For $50-$100 SendCutSend will draw it for you.

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You'll have to cut your own oil grooves but that's easy enough to do by hand.
 
arse_sidewards said:
For $50-$100 SendCutSend will draw it for you.

sendcutsend.com

Design Services | SendCutSend

Need a custom part, but don’t have CAD? Our Design Services team can help. We’ll create your file and send you a cart for purchase.
sendcutsend.com sendcutsend.com

You'll have to cut your own oil grooves but that's easy enough to do by hand.
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I can draw my own.. that's not a big deal. Just would have to find somebody to cut them..
 
Solid pics and very interesting teardown. So the lack of thrust washers in the last ones may explain those ones, but this one might have just been a fluke failure? Hmm.

Just for the sake of curiosity - To load that thrust washer, the input needs to be pushing deeper into the case (or the planetary set are driving toward the input). if you look inside the input splines, I believe you can see the back of the caged needle bearings (visible in your pic showing the inside of the input shaft, but viewed from the other side). Does that flat face have any marks like the spud shaft may have been shifting and putting pressure on it (and in turn, the input gear itself)?

I know the helical angle of the gears will generate some thrust (can't recall which direction) when torque is applied, but should be a non issue when it's freewheeling so I'm not sure that would be the culprit.

Were you just running good ole ATF in there, or any sort of mystery fluid?
 
AgitatedPancake said:
Solid pics and very interesting teardown. So the lack of thrust washers in the last ones may explain those ones, but this one might have just been a fluke failure? Hmm.

Just for the sake of curiosity - To load that thrust washer, the input needs to be pushing deeper into the case (or the planetary set are driving toward the input). if you look inside the input splines, I believe you can see the back of the caged needle bearings (visible in your pic showing the inside of the input shaft, but viewed from the other side). Does that flat face have any marks like the spud shaft may have been shifting and putting pressure on it (and in turn, the input gear itself)?

I know the helical angle of the gears will generate some thrust (can't recall which direction) when torque is applied, but should be a non issue when it's freewheeling so I'm not sure that would be the culprit.

Were you just running good ole ATF in there, or any sort of mystery fluid?
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the lack of thrust washer definitely causes some movement in it. the Input bearing cant move, so that causes the planetary to move back and forth. you can see in the inside of it where the Input shaft has hit and ground into it. My first case that is im sure 99.9% my problem. I bet the first burnt up case i had that was the problem, and when i pulled it apart there wasnt one there. So one never got put back. And then i get this case, i inspected it with a cam when i bought it, the range hub looked good, and of course it probably had a broken thrust washer and it decided to eat itself when it was put under the loads of my big ass truck. Ive tried 3 or 4 differents ATF's through out this problem. But I have ATF +4 still i think. also have a bunch of Mercon LV left over from a Ford build as well thats synthetic.
I am looking at the budget to see if can finagle new bronze thrust washers for both cases.
 
Domer said:
the lack of thrust washer definitely causes some movement in it. the Input bearing cant move, so that causes the planetary to move back and forth. you can see in the inside of it where the Input shaft has hit and ground into it. My first case that is im sure 99.9% my problem. I bet the first burnt up case i had that was the problem, and when i pulled it apart there wasnt one there. So one never got put back. And then i get this case, i inspected it with a cam when i bought it, the range hub looked good, and of course it probably had a broken thrust washer and it decided to eat itself when it was put under the loads of my big ass truck. Ive tried 3 or 4 differents ATF's through out this problem. But I have ATF +4 still i think. also have a bunch of Mercon LV left over from a Ford build as well thats synthetic.
I am looking at the budget to see if can finagle new bronze thrust washers for both cases.
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I've also thrown whatever random ATF I have at any of my tcases that haven't had clutches and they've been fine. So I was just curious for the sake of discussion, but I don't think it's related here.

I definitely agree on teh side effects of the broken/lost thrust washer, I'm just a little hesitant to believe this latest case came with a broken one. Not impossibly by any means, but a cracked/failed thrust washer just isn't something I've encountered on cases in the wild. So that plus the fact that it might have been a repeat failure mode still makes me wonder.

This thing is a manual iirc? Funny question, with your wheeling style do you ever run it right down around stalling? To the point where it starts not quite "dieseling", but almost chattering the powertrain as the engine tries to keep running? With the helical cut on the gears, I'm just thinking if there ends up being "chatter" in the power delivery, it could start slamming the input gear back and forth upon its thrust surfaces. I know this is a complete speculative stretch scenario, just thinking out loud.

Edit - Though the above scenario should effect the front box as well. Hmm
 
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AgitatedPancake said:
I've also thrown whatever random ATF I have at any of my tcases that haven't had clutches and they've been fine. So I was just curious for the sake of discussion, but I don't think it's related here.

I definitely agree on teh side effects of the broken/lost thrust washer, I'm just a little hesitant to believe this latest case came with a broken one. Not impossibly by any means, but a cracked/failed thrust washer just isn't something I've encountered on cases in the wild. So that plus the fact that it might have been a repeat failure mode still makes me wonder.

This thing is a manual iirc? Funny question, with your wheeling style do you ever run it right down around stalling? To the point where it starts not quite "dieseling", but almost chattering the powertrain as the engine tries to keep running? With the helical cut on the gears, I'm just thinking if there ends up being "chatter" in the power delivery, it could start slamming the input gear back and forth upon its thrust surfaces. I know this is a complete speculative stretch scenario, just thinking out loud.
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Yes its a manual. And it has from time to time ran low rpms... but what is coming to mind, i just rebuilt my rearend cause it ran low on fluid and burnt up my bearings. This thing would vibrate terrible on decel and i could hear it rattling the gears in the transmission.. so possibly that shock and vibration could of done it.
 
Domer said:
Yes its a manual. And it has from time to time ran low rpms... but what is coming to mind, i just rebuilt my rearend cause it ran low on fluid and burnt up my bearings. This thing would vibrate terrible on decel and i could hear it rattling the gears in the transmission.. so possibly that shock and vibration could of done it.
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Huh. Normally I wouldn't think of something like that being associated with tcase issues, but in this scenario I think there's at least a small chance something like what you described there had an impact. Especially if you could hear upstream gears chattering, indicating it might have actually been getting to a backlashed "float" point with each oscillation.
 
Fiber thrust washers are perfectly fine and when one does fail you get a whaa whaa swooshing sound that gets louder with speed. You can polish the parts and reuse them if it's not too scared up which it's usually minor damage. I've never seen a failed planetary eat a shift fork though.
There is something pushing on something.
 
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