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Apologies for a very Jeep-centered question, that may not interest everybody. Here goes:

I own a 2009 Wrangler JKU (pre face-lift), equipped with the 2.8 TD engine, Chrysler NSG370 six-speed manual transmission, and the NV241 transfer. The transfer case is directly mated to the gearbox.

This transfer is a part-time 4x4 system: the vehicle is most of the time in rear-wheel drive. When the front axle is connected, it turns at the same speed as the rear axle, which is fine on slippery surfaces and in straight lines, but quite bad when going through curves on dry roads due to transmission build-up.

Other Jeep models have full-time 4x4 transfer cases, such as the NP242 from the Cherokee XJ. These allow some slip from front to back axle, and can more easily be used in situations where one is constantly going from dry asphalt to wet snow and back to dry, often found in mountain driving in winter.

I am looking for any advice as to whether a NP242 would be a drop-in replacement for my NP241. Specifically, I am thinking of not having to modify:

  • Chassis supports and general shape of the T-box (the swap should not be immediately apparent).
  • The number of splines on the clutch output shaft (I think 23 splines?).
  • The reduction ratio, 2.72:1 is fine for my purposes (no rock-crawling).

Otherwise, a transfer case from a Grand Cherokee WJ would probably be easier to source from the breakers where I live. Any ideas on which T-case would fit the JK?

  • I asked this question of a friend of mine who is a Jeep enthusiast. He thought (but wasn't sure) that the NV241 and NP242 were externally the same. He thought it should bolt up. He wasn't positive, though, because nobody in his circle has done that swap. They go the other directions because of doing rock-crawling. He said it should work, but be aware it will be for on road use ... none of that creepy-crawly stuff. – Pᴀᴜʟsᴛᴇʀ2 Jul 31 '15 at 18:36
  • @Paulster2 Excellent news, I am much obliged to both! – ALAN WARD Jul 31 '15 at 19:20
  • Make sure you CONFIRM that before you go snagging a new/used one. – Pᴀᴜʟsᴛᴇʀ2 Jul 31 '15 at 19:22
  • @Paulster2 I will, and will also take a hard look at the operating lever linkage before cutting up my trim. – ALAN WARD Jul 31 '15 at 19:48
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I've got a NP241OR on my Wrangler, and would never downgrade myself (4:1 ratio, significantly stronger than the other t-cases), but yes you can mount a NV231 or NP242 with no modifications to:

  • Chassis supports and general shape of the T-box (the swap should not be immediately apparent).

However, the inputs/outputs of transfer cases are easily swappable, and thus what you source your NP242 from (and whether or not the previous owner made any modifications themselves, like the very common slip-yoke eliminations or spline changes to accommodate non-stock driveshafts). According to the this rebuilder, the NP242 came in both 21 and 23 spline input varieties, and doesn't look to have nearly as much variety as more common ones (see the NP241 page for an idea of how much different input/output options can vary).

All that to say you may need to adapt the input and output, but the NP242 itself will work just fine, albeit significantly weaker and with a less extreme reduction ratio.

What you should do is note the input spline count (23) of your model, and the output style, and seek either a NP242 that exactly matches, or plan on retrofitting with the proper input/output, or swap them from your NP241. Since modifications and even swaps are common, don't just assume the donor vehicle matches the OEM specifications.

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