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Old 01-25-2010, 12:23 PM   #1
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NP231J Transfer Case

Noobie here, my son's 2005 Wrangler Unlimited with the NP-231-J Transfer-case quit working suddenly while driving on the street. He does not off-road it and doesn't abuse it either.
No drive in 2WD or 4WD High, but gear noise in both, it drives in 4WD Low, also with some noise. Towed it home on a rollback.
I want to drop the t-case and try to repair it myself.
I checked the shift linkage, all is good there, not loose or damaged.

Q: How does the drive shaft detach from the t-case? Do you cut the clamp that holds the rubber boot over the end of the drive shaft? Then what?

Q: Are overhaul parts readily available for the NP-231?

It is a Wrangler Unlimited, 4.0 automatic trans, manual 4WD with about 100,000 miles on it. No problems until now.

Thanks for your assistance.

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Old 01-25-2010, 01:51 PM   #2
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The front driveshaft is bolted to the transfer case with four bolts, don't cut that rubber boot which only covers the driveshaft's slip-joint. You'll need to drop the transfer case skidplate to gain adequate access to those four bolts.

Are you absolutely 100% certain the transfer case shift linkage has not simply slipped out of adjustment? I would get underneath and while someone else shifts the lever, note how the linkage works. Then you'll see how it is held in adjustment by a 1/2" hex head bolt that holds the shift rod in position. That bolt can loosen and allow the shift rod to pull out & completely out of adjustment.

While watching which way everything moves while someone else pushes the shift lever towards 2wd, note which way the lever on the transfer case itself goes for 2wd that the rod connects to. Then, after loosening that bolt so you can do the next step, use pliers on the lever (not the rod) that is on the side of the transfer case itself to see if you can't shift it manually all the way into 2wd. It's somewhat stiff & notchy between 2wd, 4Hi, N, and 4Lo but you can shift the transfer case via that lever with pliers to insure it's fully into any of those positions. See if you can get it into 2wd with the pliers and if you can, just re-tighten that bolt so the lever on top can fully engage 2wd the next time.

Here's a pic of the linkage and you'll see that bolt I'm talking about that is circled in red. When that bolt slips & lets the rod slip, the whole thing goes out of adjustment.

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Old 01-25-2010, 03:23 PM   #3
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Thanks, that is what I looked at when I was under there. The linkage was tight and secure.
I'll check it like you said to, one on top & one underneath, with my son as soon as we can get some time off together.
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Old 01-25-2010, 05:32 PM   #4
Knows a couple things...

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Quote:
Originally Posted by WagoneerDad View Post
Thanks, that is what I looked at when I was under there. The linkage was tight and secure.
I'll check it like you said to, one on top & one underneath, with my son as soon as we can get some time off together.
The shift rod may seem held tightly by that bolt if you just push/pull on it directly by hand but it still may not be tight enough to remain in adjustment during normal use.
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Old 03-05-2010, 01:04 AM   #5
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Resolution: The T-case was fine. Turned out the plantary gears in the transmission failed which required a complete transmission & torque converter overhaul. (ouch $$)
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