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Oil Burning - Diesel Swap guide

Diesel Jeep At Top Truck Challenge
Pete Trasborg
| Brand Manager, Jp
Posted April 1, 2013

Put A Diesel In Your Jeep!

Just think about it…a built Jeep with off-idle, stump-pulling torque on 35s or 37s, pulling down 30 mpg and rolling down the highway at 1,200 rpm. Sounds pretty good doesn’t it? Yeah, we thought so, too. So we rounded up as many of the companies we could find that build diesel-swap kits or do cool diesel engine swaps that you could use for your Jeep.

We managed to find everything from a Kubota engine in a flatfender to Cummins in a FSJs to the almost-required TJ and JK diesel swaps. Now, you are going to ask if they are legal. Well, the bottom line is you will have to do that research yourself. Every state treats swapping a gas engine for a diesel engine differently, so before you go getting out the credit card, check into it.

We’ve also included mileage numbers where we could, so you can get a good idea of real world mileage after the swap. In general, though, whatever you are getting for mileage in your Jeep now, you’ll typically get 1.5 to 2 times better mileage with a diesel swap. Mileage numbers vary greatly from driver to driver and Jeep to Jeep. Will a diesel swap ever pay for itself? Well, if you were on the road every day, then yes, it might eventually pay for itself. But that is not really a great reason to do it.

Unless you get all the parts for free, and do all the work yourself, a diesel conversion isn’t going to be cheap. When you consider many of the engines in this story are $5,000 or more to get a new one, $1,000 for adapters, plus all the associated cooling and plumbing, as well as potential axle or gearing changes necessitated by the diesel engine’s weight and powerband, it’s not a cheap undertaking.

But considering the longevity of most diesel engines, the better mileage, and their operating characteristics, then a swap starts to sound a lot better. For us, it is the combination of the three reasons that we always play with the ideas. For you, here’s a bunch of companies with a lot of different ideas on how to get ’er done.

Jeff Daniels
When we first spoke with the company several years ago, it was just starting to evaluate the feasibility of putting the 3.9L four-cylinder 4BT Cummins in Jeeps and offering kits to let you pull it off. The first one we saw was a TJ Wrangler, but today Jeff Daniels Jeep Customizing offers brackets and kits to put a 4BT in everything from a ’76 CJ to an ’06 Wrangler. The company knows what kind of 4BT you will need to keep your accessories and for best front driveshaft clearance and it has designed its own vibration-isolating engine mounts. While the kits don’t necessarily include a 4BT and/or a transmission, typically the company can source these parts. However, they are located in Pennsylvania, so shipping a 725-pound engine isn’t going to be cheap. Expect around 25-35 mpg, depending on how heavy your Jeep is and how you drive it.
Information: Jeff Daniels Jeep Customizing

Bruiser Conversions
Got JK? Want diesel? Bruiser Conversions offers both builders kits and full-on installation of 4BT engines. The kit includes a transmission adapter, throttle pedal assembly, intermediate housing and flywheel, battery tray, correct componentry for your engine, power steering pump and eight-groove drive pulley. The kits also include eight-groove pulleys for your alternator and A/C compressor so that you can reuse the existing parts. The kit is currently intended for ’07-’11 Wranglers and the company even thought to include spacers or springs to level your Jeep back out. The kit doesn’t include wiring, but does include consultation and parts of the kit also work for the ‘97-’06 Wrangler. Also there is always the option to take your Jeep and have the conversion done for you as well. Get high 20 mpg in mixed driving on 37-inch tires.
Information: Bruiser Conversions

ACD Engines
If you aren’t sure where to get your Cummins engine, or don’t want to play around in potato chip trucks, ACD Engines might be for you. The company has a staggering array of new Cummins engines in stock. Just about any Cummins you’ve thought of putting between the framerails of your Jeep can be had here (and probably quite a few you haven’t thought of). If that wasn’t enough, the company also has tons of auxiliary parts. In fact, it has everything from transmissions and T-cases to turbos, ECMs, injectors, flywheels, and more.
Information: ACD Engines

Mike’s Performance
We first learned of Mike’s Performance Automotive from our sister magazine, Diesel Power and while the shop doesn’t offer kits, if you are near its Lancaster, California, location, they can certainly provide a conversion like this for you. This clean conversion in a ’93 Wrangler uses a 3.9L 4BT coupled to a TH400 automatic transmission that the owner sourced from a Frito Lay truck. Mike’s Performance got it running and driving reliably. At the time of the photoshoot, the Jeep had the factory 3.08 gears and 33-inch tires and pulled down around 28 mpg in mixed driving.
Information: Mike’s Performance Automotive

Mercenary Off-Road
Want a diesel-powered Wagoneer? Live near Camarillo, California? Mercenary Offroad can shoehorn a 5.9L 6BT six-cylinder between the frame rails of your FSJ and have it running like it was always there. The installation shown is in an ’84 Wagoneer and used a ’98 engine and 47RE transmission from a Dodge pickup to get the job done. Until the Jeep fires up, you’d never know it had a diesel in it. If you’ve got a ’63-’69 Rhino grille, you will need to choose between your classic schnoz and an intercooler. As it is, the intercooler is pretty tight to the late-model grille on this Wagoneer. And it should get around 25 mpg if you can stay out of the fun pedal.
Information: Mercenary Offroad

Aaron Reeves
Want to build your own diesel Wagoneer with a 4BT under the hood? Not a problem. Call Aaron Reeves Garage and ask about its kit. It includes liquid-filled motor mounts to kill vibration and both engine and frame-side bolt-on mounts with all hardware. Also included is a video installation guide, a transmission crossmember to work with an NV4500, TF727, or 47RH, and a liquid-filled transmission mount. If that wasn’t enough the company will include troubleshooting help for you as you install its parts if you simply shoot a video and submit it. Don’t want to do it yourself? Don’t have a Wagoneer? Not a problem, take your Jeep to the company and it’ll get you burning diesel to the tune of around 30 mpg in no time.
Information: Aaron Reeves Garage

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