NP-231 replacement

  • I just put a thread in the for sale section that I need a np-231 for my TJ, but I'm looking here for some information so that I might be able to broaden my search and find one that may not be a direct fit but could work. Or even if I can find one with a good case, I'm not opposed to switching out some parts if that would work.


    So, I know that ideally I would find one from a TJ with a 4cyl and the ax-5, but I've struck out on that so far. If I can find one that mated to an ax-15 is it just a matter of changing the input shaft? And if I can just find another one, are the cases the same between years and vehicles? Or do I really need a perfect fit here?


    Thanks


    Jamie

  • You ideally want a TJ case and swap the input if need be. Something failed in yours to cause a hole, likely the chain but a chunk of broken shift fork could have been forced through the case by the chain. I'd tear it out and split it before you can say your internals are still good.

  • I don't think the chain failed, because the jeep was still moving in 4wd when I pulled it into the garage to pull apart. But being that it wouldn't shift out of 4wd could make a shift fork a definite possibility. I actually thought it was just low on fluid until what I put in came pouring out the hole.


    Planning on pulling it out an opening it up tomorrow to see what, if anything I can salvage and reuse.


    Thanks for the information, at least makes me think I'm on the right track. Hoping to find the right one.

  • I don't think the chain failed, because the jeep was still moving in 4wd when I pulled it into the garage to pull apart. But being that it wouldn't shift out of 4wd could make a shift fork a definite possibility. I actually thought it was just low on fluid until what I put in came pouring out the hole.


    Planning on pulling it out an opening it up tomorrow to see what, if anything I can salvage and reuse.


    Thanks for the information, at least makes me think I'm on the right track. Hoping to find the right one.

    I believe the TJ version differs front the YJ in that in 2wd it moves the front output to a neutral location unlike a YJ that keeps it in high range and disengages at the axle disconnect.


    Sent from my HTC6525LVW using Tapatalk

  • Your chain is deff stretched out which wore the case down. I know Dan in west chester will have one for you, he has all kinds of cases laying around i was just there.


    610-496-1834

  • Your chain is deff stretched out which wore the case down. I know Dan in west chester will have one for you, he has all kinds of cases laying around i was just there.


    610-496-1834

    There's what I was looking for. I've been to his place before, but couldn't find the number.


    Thanks!

  • only difference in the cases from a tj is the input shaft. It takes about 2 hr to take a case apart, replace and reassemble. U just have to swap yours in.

  • I saw a 4 cylinder TJ case there myself, i know he has them but he is away this weekend

  • So any TJ case would work? I've found plenty of XJ and YJ cases, any chance those would substitute?


    Thanks

    Not sure on the YJ variant but I believe an XJ case is clocked slightly differently (or it may just be the pattern on the trans...my mind is going in my old age).


    --Ian

  • Not sure on the YJ variant but I believe an XJ case is clocked slightly differently (or it may just be the pattern on the trans...my mind is going in my old age).
    --Ian

    its the trans that is clocked diff on XJ, all t case have the same clocking you just need to make sure the input shaft is the same length and spline count

  • yj cases have a different main shaft and tail housing. Although parts swap over i would stay with a tj case. Im betting a newer xj, 97-02 wound probably be the same as a tj case

  • I saw a 4 cylinder TJ case there myself, i know he has them but he is away this weekend

    I was actually able to catch up with him and was able to grab a case yesterday. Two years newer than mine, direct replacement. Went in yesterday.


    If I hadn't effed up one of my u-joints during the repair, I'd be all set. For now it's up and running, just without a front DS until I can get another joint this week.


    Thanks all!

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