Thread: NP231 input shaft swap write up.

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  1. #1 NP231 input shaft swap write up. 
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    Don't know if this has been documented on here yet. I searched and didn't find it...so I got out the camera and did work. Obviously I had to break down two transfer cases to get the correct input shaft, but I have omited the donor np242 breakdown. I will tell you this though, it is seriously more complicated than a np231..or I just did it all ass backwards. Anyways, this is just the np231 part...I figured you can handle destroying your old case all by yourself.


    Step one is obviously removing it from the vehicle...if you can't figure this out then I really can't help you. Draining it is also a good idea, ask me how I know.



    Before you remove the case from the vehicle it may not be a bad idea to pull the front output yolk while in the vehicle...if you forget to then you will have to resort to this. Anyways, pull the front yolk.



    Next remove all of the bolts from the case halves. They are 15mm. Then look for the pry points, get a big ass screwdriver and do work. Just bust open one side, then find the pry point to the other side and bust it open. The idea being to open both sides equally.



    Open case, shouldn't have to force it too much. If it gets a little stuck just wiggle things around a bit. Should end up like this.



    This step can be done now, earlier, or even later...but it must be done, I choose to do it now. Remove the front (tranny input side) cover. Bolts are 10mm. Again, use big ass screwdriver to pry open. Be gentle...it is aluminum after all.



    Here is the first horrible snap ring, there is no fun way to remove this. It sucks even more if your snap ring pliers blow like mine do. I found that a couple of strategically placed flat head screwdrivers help here.



    Next thing you will want to remove is the shift fork. Just wiggle the little bugger around some, it will eventually get into a position where you can remove it. Might try changing from 2wd to 4wd to N.



    And it's out...



    Now you should be able to remove the planetary set (because we already removed the front cover and sna ring), twist and pull. Too easy.



    Now that the planetary is out, we need to remove another damn clip and pull the input gear. See damn clip.



    Now simply pull the input shaft/gear.



    As stated, I already broke down the 242, here are both inputs...I need the short one. It's been covered many times, but there are a few things that can differ with input shafts; length, gear cut, taper...etc. My only issue was length.



    Install proper input shaft/gear into planetary. I have no idea what these do-dads are, but don't forget them. And also, remember to install the clip, not shown.



    We are ready to put it all together again. First, clean up the magnetic thingy.



    Clean up this thing two, it's the oil pickup...the screen may be dirty.



    Reinstall the planetary containing the swapped input shaft/gear.



    Twist and drop, it will go.



    Time to install the shift fork, just like removal, trist it around some and it will go.



    Another shot of this. Put the tab in the rail, too easy.



    Properly installed, should be able to shift it into other ranges if you want to.



    Now it's time to clean everything up, can of brake clean comes in handy here. A wire brush is also helpfull, be gently, it is aluminum.



    RTV...I hate the smell of this stuff.



    This part kinda sucks. It was actually much easier to stand one up and drop the other down onto it, but that would have rendered me pictureless. Make sure the magnet thingy doesn't fall out. Once the case is together bolt it all back up. I used a star like pattern to tighten bolts. I have no clue what foot lbs should be used, I went with pretty damn tight.



    Not shown, the snap ring we took off here earlier needs to go back on. Once thats complete it's time to replace the front cover. Be carefull here, there is a depression (oil gally) on the cover that lines up with a hole (the one without threads) into the transfer case...they need to be orientated together. RTV this guy up, make sure not to RTV up the hole or depression though. Once it's all back together you ahould be able to cycle it through all of the ranges with binding or odd/excessive niose.

    After this is back on you should be done, hopefully you don't have any extra pieces laying around. Hopefully I didn't miss any major steps...it's hard for me to remember to take pictures while wrenching...I am, after all, riddled with A.D.D.
    Quote Originally Posted by Cody View Post
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  2. #2 Re: NP231 input shaft swap write up. 
    Rawr Lifetime Supporter jfowlzj95's Avatar
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    I may have missed this somewhere else, but was there a reason you swapped out the shafts from the planetary gears (like one planetary was messed up or something)? Could have just swapped the whole planetary gear itself.

    Other than that, very nice write up!
    Last edited by jfowlzj95; 09-20-2008 at 05:42 AM.
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  3. #3 Re: NP231 input shaft swap write up. 
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    Quote Originally Posted by jfowlzj95 View Post
    I may have missed this somewhere else, but was there a reason you swapped out the shafts from the planetary gears (like one planetary was messed up or something)? Could have just swapped the whole planetary gear itself.

    Other than that, very nice write up!
    The np242 that donated the input shaft was my original '93. It had 256k miles on it, about 100k of which on 33s or bigger. I spun both planetaries around, the np231 was much smoother and looked less worn to me, it had been rebuilt a while back and maintained better. That's all, I could have done what you suggested though. Thanks!
    Quote Originally Posted by Cody View Post
    I have a year round cougar permit. Cougars are always in season.
    '93/6"-Custom 3link & Tri-4link Long Arm/4.6L Stroker/AW4/np231/HP30/D44/Detrioted-4.88s/35s/murdered out wood grain playa...
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  4. #4 Re: NP231 input shaft swap write up. 
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    Nice job - good right up !
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  5. #5 Re: NP231 input shaft swap write up. 
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    Quote Originally Posted by nierace View Post
    Nice job - good right up !
    Thanks!


    So many of you have probably heard me bitching about my unusual vibrations...hell it's one of the reasons I picked up the 231 w/sye, even though I wasn't sure that I needed it. Anyways, I may have just found the culprit while reassembling my 242 (PITA by the way). The front output shaft, that the front yolk bolts up to is severely bent. I spun it while it was free in it's hole and I'm talking close to a 1/4" out...like a cheap pool stick on a pool table surface. Wow, I can't believe the damn thing didn't grenade.


    I'm no engineer, but it looks like the way the chain rides higher up on that shaft due to the design of the 242, it might put more stress on that output shaft. I guess you would have to see it. Anyways, FYI, that can happen. Also, if you scroll up a bit, you can see the inherent differences in simplicity between the 242 and 231.
    Quote Originally Posted by Cody View Post
    I have a year round cougar permit. Cougars are always in season.
    '93/6"-Custom 3link & Tri-4link Long Arm/4.6L Stroker/AW4/np231/HP30/D44/Detrioted-4.88s/35s/murdered out wood grain playa...
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  6. #6 Re: NP231 input shaft swap write up. 
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    Quote Originally Posted by jfowlzj95 View Post
    I may have missed this somewhere else, but was there a reason you swapped out the shafts from the planetary gears (like one planetary was messed up or something)? Could have just swapped the whole planetary gear itself.

    Other than that, very nice write up!

    There are two different gear cuts on the ring gear on the inside of the case. That's why you would not swap just the planetary. (unless you have the same gear cut).

    I am in the middle of this same miserable swap, and found out the hard way that lots of time when you are swapping input shafts you have to be very careful to match the planetary gears to the ring gear they ride on. Otherwise it makes a whirring sound over about 20 mph and then grenades shortly after.
    1995 ZJ Laredo - 5.2 V8, NP231 w/SYE, 5.5" lift with Clayton Longarms.

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  7. #7 Re: NP231 input shaft swap write up. 
    Senior Member Jim311's Avatar
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    I guess if anyone is interested I have a 249 input from a 96 5.2L that I didn't end up needing. The VC of the case is trash but all of the internals are fine. If anyone needs it I'd be willing to sell it. Somehow my 231 swap was completely bolt in.. seems most people were not so lucky.
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  8. #8 Re: NP231 input shaft swap write up. 
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    will the input shaft from a 249 fit in the 231? my 231 is too short and i need to put the longer one in from the 249
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  9. #9 Re: NP231 input shaft swap write up. 
    Senior Member canadian_driver's Avatar
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    good write up
    This person should be taken as seriously as a heart attack while piloting a zeppelin over a bacon factory, which is the most serious of heart attacks, because if that zeppelin crashes into that bacon factory all of us will be without bacon and that simply will not do.
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  10. #10 Re: NP231 input shaft swap write up. 
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    I guess if anyone is interested I have a 249 input from a 96 5.2L that I didn't end up needing. The VC of the case is trash but all of the internals are fine. If anyone needs it I'd be willing to sell it. Somehow my 231 swap was completely bolt in.. seems most people were not so lucky.
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  11. #11 Re: NP231 input shaft swap write up. 
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    Hi my 247 in my 99 Wj just blew, so im looking into replacing it with a 231 and seeing whats more cost effective currently. I want to know everything I will need in order to make the swap. drive shafts? input shafts? output shafts? etc time and money are not on my side currently as im also in the process of replacing my mothers 3.7 motor in her liberty and trying to finish off my lifted XJ. so please don't give me input on whether or not the swap is worth it, that ill determine on my own. I want to know everything I would need to purchase in order to make the swap work. Thanks all! any questions let me know thanks!
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