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Grand Cherokee Transfer Case Swap
Q: I have a few questions regarding my '96 Jeep Grand Cherokee. It's equipped with the 4.0L engine, an automatic transmission, and a Quadratrac four-wheel-drive system. Do you think this transfer case is trail-worthy for moderate 'wheeling? I don't use the Jeep to go rockcrawling, just for hunting and fishing trips. How hard would it be to swap an NP231 transfer case in its place? Would the Dana 30 and Dana 35C axles still be useable? I'm also considering a 3-inch lift and 31- or 32-inch tires. Any suggestions are greatly appreciated.
A: Phillip, the Quadratrac four-wheel-drive system in your '96 Cherokee uses an NP249 transfer case. Common failures in this transfer case occur within the viscous coupler, which the case requires to transfer power while in 4-Lo. One of the big issues with this system is that the front and rear driveshafts aren't locked together, which leaves the power to take the path of least resistance and go to whichever wheel is easiest to turn. This effect is commonly detected in steep hill climbs, where the vehicle weight is off the front tires. The majority of the power is sent forward, but with the weight off the front tires, there's little contact with the ground, and thus no traction. Another issue with the NP249 is the lack of an available slip-yoke eliminator kit. This will become further apparent once you lift your Grand Cherokee. Swapping in an NP231 transfer case in place of the Quadratrac unit is a common conversion, though not always a direct bolt-in swap. Most NP231 cases from Jeep XJs, YJs (different front output yoke), or TJs will work, but it's usually best to source one from a similar year to your vehicle. You'll also need to find a unit with a 23-spline input shaft that will match the length of the input shaft on your current transfer case. Mating the new transfer case to your current axles shouldn't present a problem. You also might install a slip-yoke eliminator kit on the new NP231 case at the time of the swap, if you see a suspension lift in your future. Good luck.
Lift Ideas For CJs
Q: I own a '69 Jeep CJ-5, which I would like to lift. I plan to do some off-roading with the vehicle, but nothing too serious. I was considering mounting the springs over the axles and rotating the rear pumpkin in line with the driveshaft. I was told that this would reduce vibration, but might cause the bearings to be underlubricated. I was wondering if I would have to change the steering linkage or any of the other frontend components and also what size tires and rims I should use with this modification. I don't have a ton of money, but I plan on also rebuilding the brakes and whatever else is needed to get it right the first time. Thank you for your assistance.
A: Joseph, if your CJ is currently sitting at stock height and you simply wish to improve its off-road prowess, then ditch the spring-over-axle (SOA) idea for now, and start a bit smaller. While SOA will certainly lend a good degree of improvement to your vehicle's off-road capability, it can also open up a can of worms if it isn't done correctly, and could even end up costing you more in the long run. Your cheapest option is to stay spring-under and simply invest in a quality lift kit. Most aftermarket suspension systems include everything required for installation, and many of the manufacturers also offer provisions to modify or replace weak links within the steering system. A 4-inch lift system is commonly ample for clearing 33-inch tires. A 35-inch tire is also a possibility on your CJ, but remember that bigger tires will certainly require more lift, which easily translates into more money. If you're dead set on the SOA, do your homework and talk to people who have completed a similar conversion. You'll most likely need to address the rear pinion angle and will definitely need to modify the steering system. OK4WD [(908) 454-6973, www.ok4wd.com] in Stewartsville, New Jersey, offers a variety of Jeep CJ suspension options, as well as high-clearance steering kits, tie-rod flip kits, and SOA steering systems.
We'll Take It
Q: I've been deployed in Iraq for more than a year now and have enjoyed reading your magazine out in the field. I own a '51 Willy's flatfender, which I've been restoring/modifying for eight years. I wanted to compliment you on the March '04 issue, specifically the "Vintage Steel" article on a '55 M38A1. I think it's great that with so many vehicles out there, the original vintage Jeeps are still sought after and covered in your magazine. The $20,000-plus rig that rolls into camp is good if you can afford it, but the vehicles that really impress me are the ones with bent quarter panels, Hi-Lift jacks strapped to the bumper, and a driver with a grin that says, "I made it in my $2,200 rig." That doesn't count the fun of fixing it up yourself in the first place. Thanks, and "Brave rifles."
SSG Chris Lillibridge
3rd Armored Calvary
Al Asad, Iraq
A: Chris, We'll always take a compliment. Thanks for reading. Keep up the great work over there. We'll hold down the trail for ya.