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NP231 Problems (2000 XJ)

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2000 Jeep Cherokee XJ

4.0/AW4/231, 181k


Driving down the road the jeep would make a grinding noise and loose power for a half a second like gears not grabbing. It does not grind all the time. Just randomly. It would do it when shifting from forward to reverse gears and driving down the road in 4hi and 2hi. It will not make the noise or do anything to affect operation in 4lo.


I just took it for a ride down the highway. Set the cruise at 60mph. About every 100 yards I would hear the grinding noise and the jeep would buck (loosing power to the ground). Drove for about 2 miles and all of a sudden there was LOUD grinding then no power. Pulled to the side of the road. No propel in 2hi or 4hi. I put it in 4lo and was able to crawl back home.


So as it sits now, I have no propel (no forward or reverse) unless I'm in 4lo and everything works as it should.


I'm told there was a dealer service bullietin for this back in the day, but I cannot find anywhere online to read up on it.


Of course no one on the range has a good 231 laying around! Id like to fix the one I got for a education anyway.

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Okay I found the issue. After cussing and swearing for over 3 hours, 2 trips to town for different tools, I finally got it out. (I'm slowing bringing my tool collection back from what it was before i moved out west for a few months for work and sold everything..)





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Pile of junk about the size of a snuff can lid on the magnet



So what do you guys think? Should I just replace it with another one? Or fix this one. My question now is, How did this happen? Worn chain or bearings or both? To my knowledge this Jeep has 181,000 miles on this case..


Fluid in this case was BLACK. Probably never was changed... :shake:

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Older would still need to be newer than 94 as they changed the cut of the gears that year.



you're thinking backwards from what I'm saying.



were he to swap all of the guts from a 95 and older (non sealed output) np231 with a 23 spline input into his 96 and newer (sealed output), yes, that would be a very slight concern.


however. the case itself has all of the same measurements as the old case. above and beyond that, the sole thing that would cause problems in an instance where you swap the guts from old to new using the new output shaft with the old guts, would be the ring for the planetary assembly on the input shaft.



basically...if you use '94 and older guts, you MUST swap the ring over along with the planetary assembly. but, a '96+ sealed output output shaft and housing WILL spline up properly with all of the case internals of a '95 and older case. seems to me it would just be easier to only swap the output shaft. pretty much the same amount of work either way you go about it, you just don't have to deal with swapping over the ring for the planetary assembly from the '95 and older case into the '96 and newer one.

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The second fork in the above pictures is shot, I'd be hesitant to even use the first since it is beat up some.


If the Jeep is just a daily driver and isn't lifted or anything, he can just swap in a new one from a '96+. If you plan on lifting it later on then think about what eagle said with the swaps as this will prevent you from having issues with the smaller to mid sized lifts.

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I plan to use this jeep as a DD. Nothing fancy, I plan to Run a couple inches of lift to clear the 245/75/16s I have on TJ Rubicon wheels. My 98 XJ has 4.5 inches of lift on 34s with no SYE and a stock np242 with 216k. No problems there..I just can't justify spending extra money for a SYE when its not neccessary. Or hunting down 15 year old cases. I wanna get this thing back on the road asap.


I'm seriously leaning towards a reman case. All depends on what the owner of the Jeep wants to do. I have it in my posession, have not paid a dime because we both knew there was a issue. If he will take around 600 bucks off the asking price to replace the t-case, thats going to be the plan.


My logical guess as to what happened was the teflon shoes wore, and probably worse then normal with that icky fluid in there. Finally they gave out and thats where the metal on metal contact happened.


If I do finally decide reman, and it works out, anybody have a good reccommendation for a company?

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I've got a half dozen 231 TC just laying out. Shipping would probably be a killer. However if you need any parts, let me know. I can't help but believe you can find something closer to home.:wrench:

Thank you for the offer sir.


I have no problem getting a used t-case. They are sincerely a "dime a dozen" but I do have to drive 60 miles to get them!! I just don't want to have future problems.


What would CC recommend if I came into posession of a used case.....


-split it open and inspect/change out the teflon shoes on the forks, then install


-install the lowest mileage case I can find and hope for the best



I'm still not fully understanding what the chain of events that happened in this case.. Linkage? As in mechanical connection from the lever in the cab to the case, internal problems..? I will probably never know. Its hard to know whats still good i this case being I had metal, chunks of metal floating around in there for who knows how long!

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