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T-Case died. Upgrade?


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Hey guys. I was driving to pismo beach yesterday and on the antidisestablishmentarianism my t-case died. I was just driving down the hwy and id hear random split-second grinding noises coming from the transmission/t-case area. Unfortunatly i didnt stop and didnt worry about it and all of a sudden my rpm's went up, but my truck rolled to a stop. Gears 1st-5th wouldnt engage. Fortunatly my friend was in another truck and helped me get it off of the hwy. We found out it was the transmission when we tried putting it into 4low and it would work. Ok, on to the fun stuff. I now have a chance to upgrade my t-case. I have the np231 now. Should i keep the same t-case? Or should i upgrade to a different one? I'm also thinking about dropping the peugeot transmission too and upgrading that to a AX-15.

 

BTW I have a 1987 4.0L I6.

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The 231 is a plenty strong case. I would definitely upgrade to the AX15 though. Depending on year of AX15 you may need to change input shafts on the transfer case or get a new tcase with a different input shaft. Yours should be a 21 spline (IIRC) and the newer models had a 23 spline (not sure which year they changed). The only worthwhile upgrades from the 231 would be to improve ratio from the 2.73:1 up to a 4:1 or higher case or for a twin stick case like the Dana 300.

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Haha yea.that would be a great thing to do. But right now I'm just looking for a cheap swap from pick-n-pull. unless i find a dana 300 there that is lol. Do you know what years they switched from a 21 spline to a 23 spline?

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Hard to say. There's evidence that both varieties were available at the same time during the transition years of about 90-91. Your best bet is to try and snag the trans and t-case together. Then they are a guaranteed match. :thumbsup: Any MJ/XJ/TJ/YJ after later 89 can donate its AX-15, though the YJ/TJ may need a bit of extra work.

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It will be harder to make a wrangler transmissions work because they are clocked differently so the transfercase would be parallel with the ground rather than angled down a little bit like the XJs/MJs. The XJ/MJ floor pans come down too far for a wrangler trans/case to be a direct fit so you must modify the floor pans a little bit for them to work (Time to pull out that BFH).

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Haha i guess its a good thing that the local pick-n-pull has a bunch of XJs huh? Hopefully some of them are over 89. Ill head over there soon and see if i can get an AX-15/NP231 combo. If I upgrade to an AX15 from a peugeot then I'm going to be switching from an external slave to and internal slave right? Or is it the other way around?

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It will be harder to make a wrangler transmissions work because they are clocked differently so the transfercase would be parallel with the ground rather than angled down a little bit like the XJs/MJs.

 

They're not parallel, they're just not clocked as much as the XJ/MJ ones. I believe the difference is about 6 degrees. I have one of each, I can take pics of them side by side.

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