What worked and what didn't on our project Jeep.
Even though the longer wheelbase of a Wrangler Unlimited makes it a better Jeep in our minds, there is still plenty to add that the factory never thought of or just plain left off the Jeep for cost savings. Let's face it, somewhere underneath Jeep's 50-plus-year off-road-inspired heritage is a DaimlerChrysler bean counter who calculates the cost of, and subtracts, components that enthusiasts would want. That's why over the past few issues we took an '04 1/2 Jeep Wrangler Unlimited with 200 miles on it and began our project. What we wanted was a longer-wheelbase Jeep that could climb difficult trails without worrying about component failure. We didn't want a tube buggy; this Jeep had to be something that could easily hold the family and even make trips on the road to the store if need be. In addition, we wanted it to be built with nearly 100 percent bolt-on parts. We think we ended up with just about what we were looking for.
The only major mechanical changes to the Jeep are in the suspension and axles. The 4.0L engine, 42RLE four-speed automatic tranny, and NV231 transfer case are all stock, even down to the original slip-yoke rear output. As we've mentioned in other stories, the 42RLE is a pathetic transmission. It's not necessarily weak, but it does nothing to enhance the driving experience and power output of the 4.0L in any Wrangler. When creeping in the rocks in First-gear low range with 5.38 axle gears, we could actually get the Jeep into a position where it wouldn't move or spin the tires, even with the gas pedal floored. The engine simply revved up to about 2,000 rpm and the tranny and torque converter absorbed the power and probably created massive amounts of heat. Continued use like this will eventually smoke the transmission, so we highly recommend a tranny cooler if you've added larger tires to your auto-equipped Jeep. If it were available at the time, we would have preferred the NSG 370 six-speed manual tranny. We may even swap one in eventually because this automatic is a joke, at least for our application.
If all you hit is rocky terrain, then you could opt for a lower aftermarket transfer-case gearset. The Unlimited Rubicon model has a NV241 with a 4.0:1 low-range ratio, which will work great when creeping. However, to us it's not ideal when blasting through dunes or mud. We prefer the 2.72:1 ratio since the 4.0L doesn't make crazy tire-spinning power in high range. Now, if Jeep would pony up and offer a V-8 as an option in Wranglers, the 4.0:1 transfer-case low range would be perfect since we could actually use high range with the added power.