The Petersen's 4-Wheel & Off-Road Ultimate Adventure Is A grueling, weeklong, multi-state tour of the toughest 4x4 trails in the U.S., and each year, one vehicle is built to lead a pack of the most capable trucks in the country. This time, Technical Editor Fred Williams (and his army of builders), combined a brand-new '07 Jeep Wrangler (JK) Rubicon (4-door) with an '06 Dodge Ram Mega Cab diesel and put it on top of Power Wagon axles to create a Frankenstein monster that has never existed before: the '07 Jeep Rubicon 5.9L Cummins (a.k.a. Rubi Wagon). Here's how everything came together.
'06 Mega Cab Frame Swap
It didn't take long to realize that the best way to get a full-sized Cummins into the 1/4-ton Wrangler was to use a frame designed for the power and weight of the diesel engine. Luckily, an '06 Mega Cab on its way to the crusher was found, and everything except the cab and axles were used to build the Ultimate JK. The frame was longer than necessary, so a section was cut from the middle, and a 1/4-inch plate was used to strengthen the area and notched to accommodate the Jeep body. Then, the Wrangler tub was cut and channels were added that allow the frame kickups to enter the cabin so that the body can sit flat on the Ram frame rails. Custom leaf spring hangers and body mounts were added to the Dodge frame, and before the body was installed, it got a thick coat of Lizard Skin ceramic insulation.
5.9L Cummins Swap
The experts at American Expedition vehicles specialize in swapping 5.7L Hemi v-8 engines into Jeep Wranglers, but installing the long inline-six cylinder Cummins into the JK was a real challenge. Since the ISB would not fit under the JK hood and leave room for the custom Griffin radiator, intercooler, and Optima battery, the engine was moved back 12 inches, and new motor mounts were built out of 1/4-inch steel plates. This location would also keep the front axle and suspension happy along with the added bonus of giving the Jeep a good front/rear balance. Plenty of modifications were made to the firewall and footwells with a Hobart plasma cutter, but with HeatShield wrap on the hot engine parts and a firewall extension fabricated by AEM, everything fit behind the factory Wrangler dash. brothers Dave and Jordan Harriton fooled the Totally Integrated Power Module (TIPM) that runs nearly everything in the Wrangler so that it would play nice with the Cummins. Their work was a success, and the Ultimate Adventure Jeep never lit up the Check Engine light during its 2,000-mile trip across the USA.
NV4500 And Atlas Transfer Case Swap
The team at Petersen's 4-Wheel & Off-Road insist on having the control of a manual transmission while rock-crawling and hillclimbing, so they ditched the automatic that came with the Cummins and found a nv4500 five-speed. With some help from Richard Daley of fordcummins.com the AEv team was able to find the right adapter to fit the automatic-ready engine to the manual transmission. next, the team installed a new Centerforce flywheel and high-performance dualfriction clutch. Since the engine had been moved back, the transmission crossmember was also moved back 1 foot and notched so that the Advance Adapters two-speed Atlas transfer case could be clocked down to avoid contact with the Jeep floor pan.
Axles And Driveshafts
Driveshafts from JE Reel were used because they are just 2 inches in diameter, which helps the Jeep clear rocks, but are made from strong 0.120 steel, which can take the abuse of the 5.9L diesel. The skinny shafts send the Cummins output to 91/4-inch (front) and 101/2-inch (rear) AAM Power Wagon axles fitted with selectable electronic lockers and 4.56 gears at the front and rear of the Jeep.
Superlift Kit And "Torque Fork"
In order to properly support the weight of the diesel engine, the stock Dodge Ram coils and shocks were used up front, along with adjustable Rockrunner link arms from Superlift. The rear lift blocks were removed, along with the overload leaf spring, which was replaced by a Superlift add-a-leaf spring. To prevent axle wrap, Superlift built a custom torque fork that's based on the one used in the black Diamond x-2 suspension kit. A Superlift skidplate was also used to protect the transfer case from trail damage. Since the diesel-heavy Jeep would be riding on big 42-inch tires, the team at PSC Motorsports installed a hydraulic ram-assist system that will prolong the life of the steering box and make the JK easier to steer.
42-Inch BFG Tires On 20-Inch Bead Locks
With all the frame-swapping and body modifications, (including some fender trimming), it was possible to mount the Jeep on 42-inch bF Goodrich Mud Terrain KM2 tires and keep it riding about the same height as a stock Jeep on 37-inch tires. The bFGs were installed on 20x10-inch Poison Spyder Customs SpyderLock wheels that are cast from sturdy A356-T6 aluminum. The wheels are specifically designed as beadlocks, (not cut and welded), with 6061 T-6 aluminum rings, and have a large center bore that fits easily over the Warn wheel hubs and Dynatrac Free-Spin kit.
Rollcage And Body Armor
To make sure that the Jeep (and its occupants) would not be destroyed during the Ultimate Adventure, the JK was fitted with every type of armor available. The Wrangler had just 200 miles on the odometer when it went to Twisted Customs, and the staff tore out the interior, cut off the factory rollcage and built a custom 6-point cage out of 13/4-inch steel tubing. Fab Fours supplied heavy-duty bumpers made from 3/16-inch steel and 13/4-inch tubing, providing a secure home for a Warn winch. Rock sliders from Poly Performance use 3/16-inch plate to protect the rocker panels, while AEv corner guards help the body remain intact, and an AEv vented hood keeps the Cummins running cool. Tube fender upgrades by Poison Spyder Customs give the 42-inch tires plenty of room to move. For paint, Shadow Coatings sprayed the exterior Army Green, and to protect the interior and make it easier to clean, the entire body tub was covered with Rhino Liner. Then, baja RS recliner suspension seats with bestop covers were installed up front, and a set of two low-back Rubicon suspension seats were put in the back. Sliding storage drawers from Slee Off Road, a 12-volt ARb fridge/ freezer, CO2-filled Powertanks, Mastercraft grab handles, and a rechargeable HalGuard extinguisher from H3R helped prepare the interior for the 2007 Ultimate Adventure.
The Ultimate Diesel Adventure
With so many modifications needed to build the Ultimate Diesel Jeep, you might expect parts to break on every trail, but during the entire 2,000-mile trip, the only thing that snapped was a stock Dodge front axle shaft. The Dynatrac Free-Spin kit made it easy to access the broken parts, and after a new driveshaft was grabbed from the sliding drawers, the Cummins Jeep was back on the trail in no time-with no other major problems. To learn more about the 2007 Ultimate Adventure and see additional photos of the Ultimate Diesel Jeep in action, go to www.4wheeloffroad.com.