I am in the planning stages for a smaller all-wheel drive XJ. I’m thinking aluminum LS, 6L80, and am stuck on using a part-time versus full-time transfer case in a 2001 Cherokee. I drive where there is the possibility of bad weather and bad roads about half the year, and I am concerned about the road manners of a part-time transfer case on slippery pavement. A second consideration is the “sleeper” SRT8 possibilities in an XJ. I really am leaning toward the full-time box. Axles are stock low-pinion Dana 30 and Chrysler 8.25 with 3.55 gears. Both have recently been rebuilt with TrueTrac differentials.
What Chevy transfer case should I look for if going to full-time? Will these axles hold up to the additional power? I am running stock-sized tires and am not hard on parts. What are the handling and longevity ramifications of a swap like this?
Your build is an interesting proposition: V-8 power in a lightweight all-wheel-drive Cherokee would be a lot of fun! Shoehorning a V-8 under the hood of an XJ is difficult, but it’s doable, and with a low-profile intake manifold from a Camaro, GTO, or Corvette the LS engine would actually be an easier fit than a Gen I small-block Chevy.
As for your transfer case options, you have several potential avenues to achieve what you want. While the NP231 transfer case is the best known and most common in Cherokees, XJs also came with the NP242 transfer case. It offers a full-time four-wheel-drive mode in addition to traditional 2-Hi, 4-Hi, and 4-Lo. These are very popular in snow country and are generally regarded as being as strong as an NP231 in stock form. They are plentiful in wrecking yards and easy to rebuild, and there’s even a slip-yoke eliminator kit available from Tom Wood’s Drive Shafts (4xshaft.com). Both Novak (novak-adapt.com) and Advance Adapters (advanceadapters.com) offer adapters that facilitate mating an NP242 to a 6L80 (the round six-bolt pattern is the same, but input diameter and spline counts are different). With a stock LS, you are in the upper range of what a Jeep NP242 can handle, but it should survive as long as it’s not subjected to much abuse.
Adapting a Jeep case is easy enough, but a couple of other options are available that happen to be stronger. A version of the NP242 was also used in Hummer H1s and H2s. Though similar in many ways to the Jeep NP242, there are some significant strength and durability differences, including a stronger six-pinion planetary set, a thicker chain, and an integrated cooling system. Rated for significantly more torque input, these differences also make many of the internal components different. The GM versions also don’t have a 2-Hi option, and to our knowledge the H2 versions were all electric shift rather than a traditional lever. Information is a little vague on what interchanges between the GM and Jeep versions and what doesn’t, so it’s unclear if a Hummer NP242 could be converted to run in 2-Hi and manual shift (we would be willing to bet it’s possible). Most Hummer NP242s were used behind 4L80s, but there were also H2s with 6L80s right at the tail end of Hummer production in 2008-2009. It might take some digging, but you could find a stock 6L80/NP242 combo with no aftermarket stuff required (other than a transmission controller). Heck, you could nab the entire drivetrain out of an H2 and have a complete 6.0L LS package. Plucking the entire drivetrain from an H2 donor would also eliminate a lot of common swap problems, including spline count differences, speed sensor inputs and locations, and much more. A complete H2 LS combination with a 4L80E is much more common, but if manual transfer case shifting is a requirement, you’ll want to limit your hunt to H1 transfer cases and adapt as you see fit.
As for your axles, you’re going to find it difficult to have 300-plus horsepower on tap and not use it. The Chrysler 8.25 would be a ticking time bomb with that much power even with stock tires, and why would you go through all the trouble of a drivetrain swap only to baby it due to weak axles? At minimum we’d swap in a Ford 8.8 from an Explorer. Anything more than stock-height tires would put the front axle in danger as well, and the TrueTrac in the front is going to make the Jeep drive funny in full-time mode. ,