The electrical portion of the build would have been a nightmare for sure if it wasn't for the expertise that AEV has with Jeep and Dodge vehicles. Brothers Dave and Jordan Harriton have been working on everything from making the newer Hemi V-8s run when transplanted into Jeep Wranglers to building modules so that the traction control in the Jeep Grand Cherokees and Commanders still works correctly when those vehicles are modified. The current electrical system in the Jeep Wrangler is referred to as a Can Bus network system where there are numerous computers talking to each other and sending electrical messages over the wiring harness thousands of times per second. Included in this system is a primary computerized fuse block known as the Totally Integrated Power Module (TIPM), which helps monitor and disperse power to all the different modules and engine components throughout the Jeep. However, along with this communication from each component where things like the radio, stability control, ABS, and powertrain control module report back their own performance, there are also messages between modules where they identify themselves and each other. So if one computer goes down, when it resets the other computers will tell it who it is. Thus as we were putting a Dodge engine into the Jeep body all of these computers were more than a little bit confused. To start, Dave Harriton sifted through pages of the electrical manual for both the Jeep and the Dodge before modifying the wiring harness to accommodate the diesel engine, Power Wagon lockers, and diesel fuel pump.
Once the wiring was sorted out, Jordan stepped in and did his Geek Squad job on the multiple computers across the network within the Jeep. To simplify it for us he explained that the Jeep now thinks it has a Cummins diesel under its hood instead of the original 3.8L V-6 gas engine, and it also recognizes the four-wheel drive and 42-inch-tall tires and runs accordingly. Imagine it is like a giant office building where every desk knows what they do and what the other desks should be doing, then if you remove one desk and add a new desk you need to get all the other desks in order so they are not only reporting what they are doing, but also inviting the new desk to work amongst them. It's pretty amazing but also pretty complicated from the good old days when you just need 12 volts for lights, ignition, and your winch. In the end we drove this Jeep with no "check engine" lights on the dash at all. Of course the seatbelt light was blinking because we swapped to race harnesses, the airbag light wasn't happy because we changed to aftermarket seats, and for some reason the parking-brake light wouldn't go off, but otherwise the dash was warning-free the majority of the time.
Our front suspension is a mixture of stock Dodge Mega Cab front coils with shocks and Rockrunner link arms from Superlift suspension. The tubular Rockrunner links are adjustable for caster and suspension tweaking if need be, while the Dodge coils provide plenty of support for the 1,100-plus-pound engine, yet keep the whole Jeep low for stable performance off road. | 
In the rear we kept the Dodge Mega Cab leaf springs but removed the factory blocks and some of the overload springs. We found that this made for a nice soft pack, but we eventually added a custom Superlift add-a-leaf for a bit more rearend support. Tune in next month to see the special Torque Fork Superlift built to help deal with any axlewrap from our big torque diesel. |
The Jeep JK uses a long tank that runs down the passenger-side framerail, however the Dodge frame we used is slightly narrower and the passenger side is reserved for the diesel exhaust. Lo and behold, a Jeep TJ rear fuel tank fit quite well behind the rear axle. The Jeep JK has a deep pan in the rear of the tub for storage, but we simply cut that out and stuffed the tank up under the rear bed of the Jeep. Even more amazing was how the in-tank fuel pump from the diesel Mega Cab seated in the TJ tank almost perfectly. | 
After the frame was finish-welded and painted, we dropped the engine and gearboxes into the shortened Dodge frame. Note the cable shifters for the Atlas transfer case to easily shift from high range into 3.8 low. The Atlas from Advance Adapters has become the benchmark in aftermarket transfer cases and we have yet to be disappointed in any we've installed. They're designed originally as a beefed-up Dana 300, and we have run them behind big-blocks and with up to 49-inch-tall tires. |
Running from the Atlas to the Power Wagon axles is a set of driveshafts from JE Reel. The driveshafts are just 2 inches in diameter to help keep them clear of rocks, but they are made of 0.120-wall tubing for strength. We used 1350 series U-joints at the Atlas and front pinion, while the rear Power Wagon 10 1/2-inch axle uses a flange to a 1410 U-joint. By the way, that rear axle is similar in size to a GM Corporate 14-bolt with 30-spline 1 1/2-inch full-floating axleshafts, but like the front it is fitted with the AAM electronic selectable locker. | 
A Cummins diesel is not the quietest powerplant, and with the turbo and exhaust running right next to the passenger's feet, we opted for some quality heat and noise insulation. The turbo was wrapped in a heatshield and the first few feet of exhaust were also wrapped in exhaust wrap, both from HeatShield Products. Additionally the firewall was covered in adhesive-backed heatshield mat also from HeatShield Products to keep noise and high engine temperatures away from the occupants in the Jeep. |
One of the major hurdles was getting the Cummins 24-valve common-rail diesel engine to run properly. Since it arrived with an automatic transmission behind it, we needed to purchase a new computer that was then programmed with the manual transmission parameters. If you don't have the skills or funds to take on a project like this, but you still want to swap in a big diesel, we might suggest looking at early 12-valve Cummins diesels that can be run with as few as three wires. | 
In addition to making the Jeep run, we also needed a way to make it stop. The Wrangler comes with a standard brake booster powered by engine vacuum. However the diesel Mega Cab is outfitted with a hydro-boost system where the brakes are powered off of the power-steering pump since diesel engines do not offer the vacuum required for proper braking. We looked into aftermarket vacuum pumps, but decided instead to graft the Dodge hydroboost onto the Jeep firewall, as well as integrate the factory antilock brakes. The resulting brake system with the Dodge Power Wagon discs at all four corners was excellent, even with big tires. |
And so with the engine wired and brakes and fuel plumbed, we finally had a chance to crank over the oil-burning beast under the hood of our JK. Unfortunately there is still much more work to show, like the custom Griffin radiator and intercooler, but not enough space this month to show it. Tune in again in 30 days when we cover the Fab Fours Jeep bumpers we attached to the Dodge frame, the fresh coat of 60-year-old paint, and all the little things like bead locks, winch, seats, and safety gear. Plus we'll show you how we made these prototype 42-inch BFGoodrich Mud-Terrains fit on our Jeep while keeping it the same height as your average lifted Wrangler on 37s. | |