So where were we? In the last three issues of 4-Wheel & Off-Road we've been building up an '07 Jeep Wrangler JK for our annual Ultimate Adventure trip. U.A. is the week-long off-road trip we do every summer, and as usual we're building an over-the-top 4x4 to lead our group of 20 rigs. Now if you look elsewhere in this issue you'll see the completed Jeep running the trails in Texas, but due to the magic and mysteries of magazine edit, this is a behind-the-scenes of how we built the Jeep for the trip. To catch up any stragglers, we started with a two-wheel-drive, four-door Wrangler and took it to get a custom rollcage done at Twisted Customs, then we drove it to American Expedition Vehicles (AEV) where we began combining the channeled Jeep body with a shortened Dodge Mega Cab frame since our plan included a Cummins diesel engine to repower our Ultimate Jeep. It all sounds simple when written out like this, but in fact the crew at AEV spent more than 400 man hours cutting the Jeep body to fit over the frame and drivetrain, plus the engine was moved backward approximately 12 inches to fit under the hood better, not to mention all the messin' about with wiring, plumbing, and suspension to get it just right.
Before assembling the engine...
Before assembling the engine and transmission we determined that we needed to rotate the '06 starter to clear the firewall. Luckily we could turn the starter, reuse two of the mounting holes, and then have a threaded bung welded to the adapter to install the third starter bolt.
In addition to the Cummins engine, we installed an NV4500 five-speed manual transmission-because we feel Jeeps should have manual transmissions-and a two-speed Atlas Transfer case, both of which were supplied by Advance Adapters. Also this month we'll cover the installation of a set of AAM axles from the new Dodge Power Wagon. We chose these axles because they will bolt right into the Mega Cab suspension, plus they are fitted with selectable lockers front and rear and 4.56 gears which should work perfectly with our new 42-inch BFGoodrich tires. Yes, there are some new treads on the market and we happened to get our hands on the very first set of 42s from BFGoodrich. As you can see, this Jeep buildup is quickly getting out of hand and surpassing the basic build that most of you will ever attempt, but hey, you've got to admit it's pretty cool. Take your basic Jeep, add all the coolest parts Dodge and Jeep have to offer, and what do you get? A bit more than a Rubicon Wrangler and even a bit more than a Dodge Power Wagon, It's the UAJK, but we call it the Rubi Wagon.
 The Cummins engine uses a...  The Cummins engine uses a special adapter plate between the block and the bellhousing and is different depending on the year of the engine, the style of starter, and the transmission. Luckily Roger Daley from FordCummins.com helped us sort out what would work best. Daley has made quite a business helping Ford truck owners repower to Cummins Diesels and so we recruited him for some knowledge to help in our buildup. In the end we used the new thick adapter for a manual transmission (left), instead of the thick adapter for an automatic that the engine came with (middle). |  Next we bolted the Centerforce...  Next we bolted the Centerforce dual-friction clutch to the correct Centerforce flywheel. Some of the tools we used on this buildup were a set of cordless impacts and ratchets from Ingersoll Rand. These battery-powered units have both 14.4- and 19.2-volt batteries and are available in a full line of tools, though we mostly used the 3/8- and 1/2-inch drive versions-quite handy for both shop and trail repairs. |  Most years we install the...  Most years we install the bulletproof Dynatrac Axles in our Ultimate Adventure vehicle, but this year we wanted to try something different. We've never had any issues with the Dynatrac parts, we just thought a change of pace was due, and sticking to our Jeep/Dodge theme we chose a set of American Axle Manufacturing (AAM) axles that come in the new Dodge Power Wagon. The front axle is a 9 1/4-inch ring gear with 33-spline axleshafts and a selectable locking differential. In fact it's a bit smaller than a Dana 60 which has a 9 1/2-inch ring gear and 35-spline shafts, but it is also found in the 3/4- and 1-ton Dodge Ram's equipped with the Cummins engine. |
 However, one change we made...  However, one change we made to the front axle was upgrading to the Dynatrac Free-spin kit. This replaces the costly unit-bearing and upgrades to a rebuildable hub and spindle. Also the Dynatrac kit has the tone ring and speed sensors included in the new hub and spindle so that the ABS brakes and computer are all correct and compatible. We can now run selectable hubs on the front axle. Selectable hubs mean the front axle is not turning when driving on the street, and though we are running Warn premium hubs for now, we are going to test one of the first sets of Dynatrac's own Dynaloc selectable hubs on the JK in the future, so watch for a complete install on those in an upcoming issue. |  Another upgrade we chose was...  Another upgrade we chose was a front differential cover from Fab Fours. The Fab Fours cover is fabricated out of 1/4-inch-plate steel, and makes the factory unit look like an origami paper sculpture. We like the fact that it's steel and not cast because we can weld tabs onto the cover to mount our PSC steering ram. Also note the electronically actuated AAM front locking differential. The locker is controlled by simply sending 12 volts to one terminal and grounding a second terminal that activates an electromagnet and pulls a collar together, positively locking the differential so power is delivered to both wheels simultaneously. |  The front knuckles look modified...  The front knuckles look modified because we had previously removed them and had the steering arms lengthened by Knoll Racing. Most Dodge trucks use an inverted Y steering setup where the drag link runs from the steering box to the passenger-side knuckle and the tie rod runs from the driver-side knuckle to the center of the drag link. This system works, but it's difficult to incorporate a hydraulic ram assist to help with the massive 42-inch tires we'll be bolting on. We got the crew at Knoll Racing to TIG-weld additional plates to the knuckles to gain true crossover steering where the tie rod will run from knuckle to knuckle. |