The least favorite locker...
The least favorite locker on paper turned out to be the most reliable and durable. The TFS air-actuated units were later changed to electrically actuated units in 2007, but the locker itself has remained essentially unchanged.
The next year, Yegge and Gabriel upped the ante, adding ARB Air Lockers front and rear to the one special Jeep in the Rubicon Trail executive fleet. Now they had to pry people out of the upgraded TJ. These had stock tires and wheels, and nothing else changed. Just a demonstration of off-road technology without putting a completely built Wrangler in the mix, which would have been easy for the executives to dismiss. Yegge and Gabriel now had the attention of the decision makers...there might be a better Jeep yet.
The sell job was getting the vehicle in its element and showing how well it worked. This approach of building what was essentially the first prototype before presenting the business case was unheard of. And Yegge actually paid for some of the components on his credit card and worked on components or vehicles at home to make it happen. But it was the only way to get something like the Rubicon package through the system. Once people experienced the hardware, there was no further convincing needed.
The Original Rubicon Plan
With two years of executive Rubicon trips under their belts and a growing fan club for the capabilities that these mildly modified Wranglers provided, Yegge and Gabriel sat down with another Jeep enthusiast within engineering, Jim Repp, and scribbled out the parts list. They knew the right thing to do, but kept coming back to what they thought would be allowed.
The original rear disc brakes...
The original rear disc brakes were one of the very few parts borrowed from another platform. They were originally used on the ZJ.
Eventually, they came up with three different lists of what a Wrangler off-road package might include:
1. A sticker and different colored shocks2. Larger tires, limited-slip differentials in the axles, a sticker and different colored shocks3. Dana 44 axles (high-pinion front), selectable lockers, 31-inch mud-terrain tires, 1-inch suspension lift, fixed rear output shaft, rock rails, rear disc brakes, a 4:1 transfer case, larger tires, a sticker and different colored shocks
The first two choices had been done by the Dodge team on the Ram, so the trio thought they could probably get these through the system if nothing else. But option number three was the one they knew should be built. Ultimately, it was the only option presented.
You'll notice they got everything on the list except the 1-inch suspension lift and the high-pinion front axle-nothing short of a miracle! And the high-pinion axle wasn't axed by management, but wouldn't physically fit when the first official prototype was built. It was unheard of for such radical equipment to be approved for a production vehicle program.
The original Rubicon came...
The original Rubicon came on 245/75R16 (31-inch) Goodyear MT/R tires. Getting a mud-terrain tire to pass internal standards for quietness and ride and handling was impossible, so the team ignored the rules. Starting with the JK, 255/75R17 (32-inch) BFGoodrich Mud-Terrain T/As are the only tires available on Rubicons.
Signed Off, but Far From Done
Now the project had executive blessing, funding and people to work on it. But developing the Rubicon was anything from an easy, downhill ride. The engineering team couldn't borrow from existing Chrysler Group vehicles for components because the parts just didn't exist. And very few aftermarket parts are made under the type of constraints required by a major vehicle manufacturer.
Everything was unique, and everything required a different approach. For example, the team looked at four different selectable lockers. Remember, this was nine years ago - how many selectable lockers were you aware of then? Ironically, TFS was the one design that the team didn't want because it was air-actuated and it was made in Japan. To do the initial testing, the team outfitted Wranglers with all four types and beat on them until they broke. Well almost all - the TFS lockers were the only ones they couldn't break.
Speaking of testing, neither the typical "drive it on a test track for 150,000 equivalent miles" nor any amount of virtual testing was going to cut it. The team spent months dragging prototypes to various off-road locations in the U.S. and treating them like red-headed step children. Sometimes the goal was to beat on the vehicle until something broke to find out what the weak link was.
 A fixed rear output shaft...  A fixed rear output shaft in the 4:1 geared T-case was one of the few things that wasn't a battle. The team simply created justification for fixed output, talked their way through it without much documentation and it pushed it into production. |  During one of the extreme...  During one of the extreme real-world tests of the Rubicon, the engineers found out that if you aired one high enough, the front axle would actually hit the oil pan. So the production Dana 44 has a 100-millimeter steel disc welded to top of spring pad, under the jounce bumper landing pad. |  The '03 Jeep Wrangler Rubicon...  The '03 Jeep Wrangler Rubicon was the first of what will be remembered as the most capable Jeep ever manufactured. More than 100,000 Rubicons have been produced. |