93 ZJ NP 231 Transfer Case Questions - JeepForum.com
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post #1 of 4 Old 08-09-2002, 09:57 PM Thread Starter
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2000 XJ Cherokee 
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93 ZJ NP 231 Transfer Case Questions

We bought a 93 Grand Cherokee pretty cheap recently. It needs to have the AC fixed and seemed to be bucking quite a bit when you turned the wheel left or right in 4WD.

We pulled the transfer case and opened up the casing this evening. The chain is pretty stretched and drags on the bottom of the case when not under tension. It is so loose it tries to bind up on itself and this may be part of the problem (had heavy clunks when we turned the wheels one way or the other)....but I have also been told it could be the viscous coupler. We bought the Jeep used and there was no fluid in the transfer case when we checked it. Problem is, I have never seen a viscous coupler before and my trusty Haynes manual does not show a viscous coupler. There is a drum shaped unit at the front of the mainshaft, but Haynes calls this the low range gear. Which is correct and which do you all think would cause the big clunks when we turned the wheels? I have not pulled the mainshaft yet.

We found a transfer case rebuild kit for $109 online and a replacement chain for $62. My 16 year old and I are having a good time so far, and if any of you can help out with some expert advice, we would certainly appreciate it. With costs to buy a rebuild around $800, we can certainly save a ton of money doing it ourselves (even if it takes several times !!)

Thanks in advance.

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post #2 of 4 Old 08-10-2002, 12:31 PM
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There are only two cases that came in the '93-'95 ZJ: a NP249 full time case and a NP242 that only came in the 4.0l base model. All others got the NP249, to the best of my knowledge. If you are getting binding as you turn, that is normal proceedure for a shot Viscous Coupler (as you stated), meaning you have the 249 case. There are a two ways to resolve this problem.

1) Rebuild it
2) Replace it

#1 is fine if you think you can buy all the parts for cheap and re-assemble it yourself. Unfortunately the VC is like $700 from the dealership by itself, and if you buy a used one from a xfer case shop, who knows how long it'll last

With option #2 you have a choice of going with a privately owned case (I highly recommend) and a wrecking yard case (not such a great idea, IMHO, unless you can tear the case down and ASSURE that everything works BEFORE you buy it).

Personally, I'd look around the for sale section on Jeepsunlimited.com and see if anyone upgraded their 249 to something else BEFORE it started giving them trouble. There is also www.jbconversions.com who can get you a NEW 231 case for $800. George at Transfercases Unlimited in New Jersey is a huge help as well. JU has a plethora of info, so make sure to check that site out before you start in.

Good luck to you!!!


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post #3 of 4 Old 07-28-2003, 03:09 PM
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I am going to do the the np249 to np231 swap because i am sooooo tired of the AWD! Does anyone know what the input shaft length is and the spline count? Will the np231 bolt right up or is there some modification that has to be done?
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post #4 of 4 Old 07-29-2003, 11:43 PM
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Hi Glen:
There has been discussions at length about this at JU and NAGCA.com, so check out the archives. My understanding is that Jeep used three different input shafts on their muriad of various transfercases over the years, and the ZJ tranny requires the longest one...so if you are getting a 231, try and get one from a later model TJ (I bought a case from an '01) so that the shaft length is the longer one, saving you from having to split the cases and make a mostly useless full time case with a short shaft.

Hope that helps,

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