Click for Coverage
Exclusive Content
Original Shows, Motorsports and Live Events
Try it free for 14 days
Due to the EU’s Global Data Protection Regulation, our website is currently unavailable to visitors from most European countries. We apologize for this inconvenience and encourage you to visit for the latest on new cars, car reviews and news, concept cars and auto show coverage, awards and much more.MOTORTREND.COM
  • JP Magazine
  • Dirt Sports + Off-Road
  • 4-Wheel & Off-Road
  • Four Wheeler

2017 Ultimate Adventure Vehicle’s CJ-6 Tubs Meet Modified JK Unlimited Frame

Posted in Ultimate Adventure: 2017 on May 19, 2017
Share this
Photographers: Verne SimonsTrenton McGee

You’ve heard the expression “You gotta crawl before you can walk,” right? Well, when you are building a major project vehicle essentially from scratch, you gotta horde parts before you can build.

We had already accumulated a full PSC hydro-assist steering setup for a JK, a pair of awesome Ultimate Dana 60 crate axles, a quintet of 38x13.50R17 Falken Wildpeak M/T tires, a Ranger Overdrive and SM420-to-Dana 300 from Advance Adapters, and a humongously strong and versatile Offroad Design Magnum Box four-speed transfer case setup. But the final, most critical drivetrain part had yet to arrive. So, while we were waiting for the supercool R2.8L four-cylinder Cummins turbodiesel to arrive, Verne Simons began disassembling the ratty 1971 CJ-6 tub that Hazel unceremoniously dumped in his shop. Off came the Meyer’s cab, fenders, hood, and grille. The fenders, truth be told, were about as soft and floppy as a well-worn jean jacket from the same era. And the hood, while awesomely patina’d, might not even make it to the final stage of this build.

As for the body install, although we could’ve gone the easy route and just welded the bottom of the floorboards right to the JK framerails, we have never been ones to take the path most followed. Check out the progress so far. Next time we’ll be dropping in the Cummins R2.8L and showing you how to mate it to an AMC-pattern bellhousing with some cool products from Axis Industries. Until then, get your freaky patina fix on.

We pried Fred Williams away from the throngs of autograph-seeking Dirt Every Day fans and put him to work cutting all the factory JK body mounts off the JK Unlimited framerails. If you recall, Verne Simons shortened the frame 9 inches to better fit the 107-inch wheelbase we are shooting for.
The big 38-inch Falken Wildpeak M/T tires didn’t play well with the stock CJ rear wheel opening radius. Simons’ solution was to ingeniously comp-cut the tub and hilariously text Hazel a photo. Hazel hates comp-cut Jeep tubs. Before Simons was reassigned to permanent Alaskan wintertime duty, he texted this image with the cut portion modified and welded back in. The resulting arch will just clear the 38-inch Falkens at full stuff. We love how the top bow indent no longer lines up. Symmetry is dull.
We like our rigs to sit low. We loved the overall stance of this test fit but quickly realized the Jeep would sit much taller after we brought the suspension up from full bump and actually centered the axles inside the tires. We didn’t want to give up tire size, suspension travel, or breakover clearance underneath for a low stance, so we decided to drop the body down several more inches on the frame instead.
Simons made careful measurements and determined which portions of the floor were making the tub hover high atop the framerails, shooting for the top of the JK framerails to just sit flush with the tub floor. Out came the saber saw and cutoff wheel.
East Coast and Rust Belt folks are no doubt cringing at the sight of a relatively solid early Jeep tub floor getting chopped, but hey, if you wanna make an omelet you gotta break a few eggs.
We laid the chopped tub back atop the JK frame and took stock of the situations. The tub now sat a good 3-4 inches lower on the frame. We toyed with the idea of modifying the floor to weld back in, but Hazel thinks we should go with some leather or heavy canvas material that will snap in just to keep stuff from falling straight through to the ground. We’ll do some more head scratching and come up with a plan by next time.
Out back, the rear suspension crossmember pokes through just a couple inches. Again, some leather or heavy canvas on snaps will be removable for servicing the shocks and will help keep stuff from falling out of the tub, assuming the boss-man gets his way.
Even shortened 9 inches between the axles, the JK frame had an enormous overhang. Just goes to show you how much larger a JK Unlimited really is compared to an early Jeep, even a long-wheelbase CJ-6. We marked the frame where we wanted to cut and then pulled the tub forward out of the way.
The offending overhang was cut off with a saber saw. We will build a rear bumper that we can weld straight to the JK framerails and that can serve as a rear recovery point.
Hazel had planned on keeping the rollcage that was in the Jeep when he bought it, but then Rob Bonney (owner of Rob Bonney Fabrication) came by Simons’ shop to check the progress. Bonney took one look and spotted a bunch of bad stuff we hadn’t noticed, like brazed welds and other horribly unsafe issues. Simons promptly headed to Rob Bonney Fabrication and drew out floor plates in SolidWorks for a new ’cage.
With the new floor plates cut out of heavy steel, we add a new, safer ’cage build to the knock list. We are still planning on retaining the factory low-back buckets, though, but we may add a padded headrest mounted atop a crossbar—or not. We’ll see.
While Bonney was loaning time on his cutting table, Simons drew up some body mounts and cut them out of plate steel and brought them home to weld up. That is where we’ll leave the body shenanigans this time.
Here is a sneak peek at the future, as 4WOR contributor and Ultimate Adventure crony Trent McGee studies the Advance Adapters instructions on how to sandwich Hazel’s SM420 transmission between the Offroad Design Magnum Box and the Advance Adapters Ranger Overdrive. This thing should have more gearing options than a Unimog. And all with Cummins turbodiesel power and mileage!


Miller Electric
Appleton, WI 54912
Skyjacker Suspensions
West Monroe, LA 71294
Falken Tire
Fontana, CA 92335
Offroad Design
Advance Adapters
Paso Robles, CA 93446
Cummins Inc.
Columbus, IN 47201
PSC Motorsports
Azle, TX 76020
Rob Bonney Fabrication
Axis Industries

Connect With Us

Newsletter Sign Up

Subscribe to the Magazine

Browse Articles By Vehicle

See Results