Dakota Customs is building "Dakota," a 2014 JK Wrangler Unlimited using Currie Enterprises' new JK high pinion 44 frontend and a Rock Jock 60 rearend. The Jeep also features Currie's JK suspension and 37-inch Mickey Thompson Baja Radial ATZp3 tires mounted on American Racing Outlaw II wheels. As this was originally going to be our vehicle, but is now going to be a feature in 4Wheel Drive & Sport Utility Magazine, I was involved when choosing parts for the build.
JK Wranglers with the anemic 3.8L V-6 and 42RLE automatic transmission called for the lowest gears possible when being built. 5.38s were usually the ratio of choice. When the new 3.6L and WA580 automatic appeared in 2012, we kept building them as we did the older JKs. Many found the 5.38 gearing was too low, as the WA580 has a 3.59:1 first gear (compare to the 42RLE's 2.84:1 first gear). With the Rubicon's NVG241OR 4.0:1 low range, the new JK Rubicons are low-geared when running 37-inch tires.
You'll be reading about Lucky '13, the 2013 JK Unlimited Rubicon built by Currie Enterprises starting next month. That Jeep was ordered by Classic Motors in Richfield, Utah. It was a fully optioned Rubicon—with one exception—it came with 3.73 gears. Currie was installing new front and rearends, anyway, so the OE gearing didn't matter. During the long drive home, it became apparent that the 3.73s were working very well in the stock Rubicon with 32-inch tires. Fuel economy was excellent, much better than my 2012 with 4.10s returned when it was unmodified. In low-range First gear, the Jeep was still very low, but in Second gear low range I could get some wheel speed and momentum when starting out.
Some thought went into ordering gears for the 2014. With 37-inch tires, the exact same ratio as what the Jeep had with 32-inch tires and 3.73 gears was 4.31. Taking into account the added diameter and mass of the larger tires, 4.56 gears should work great. No one agreed. Some said 5.13s were the way to go and others, still trying to build a 2007-2011 JK, suggested 5.38s. Yukon 4.56 gears were quickly waiting for installation into the Currie front and rearends.
Dan McKeag and the team at Dakota Customs soon had the 2014 JK ready to drive. Dan called from the highway and reported the Jeep ran smoothly and quietly. I asked how the gearing was, and he replied it felt excellent. The heavy Unlimited had plenty of power off the line and was turning about 2,800rpm in overdrive at 80 mph. Perfect.
When the JK arrived on the scene in 2006, we immediately went to work installing parts that worked on the TJ Wrangler and turned our JKs into Jeeps that performed like TJs. It's natural to apply old solutions to new designs, but we shouldn't do it.
Don't keep building the last generation of vehicle when starting a project on a new one. No matter what the naysayers tell us, 4.56 gears work when running 37-inch tires on the 2012 and later JK Wrangler and Wrangler Unlimited equipped with an automatic transmission.
Watch for the complete feature on Dakota soon.