A Gear for Any Occasion: 2017 Ultimate Adventure Vehicle CJ-6 Gets the Old 5-Shifter Drivetrain

    Part 4: A Gear for Any (And We Mean Any) Occasion

    Verne SimonsPhotographerChristian HazelWriterTrenton McGeeWriterTrenton McGeePhotographer

    Editor Hazel is a total control freak. We are not talking about enforcing employee dress codes or tracking how on-time stories are turned in. Nah, we mean in terms of how he likes his vehicles set up. Some UA vehicles have really gone over-the-top in terms of complexity. But for Hazel’s rig he insisted on a healthy dose of analog with a heaping side of manual control. Outside of the small, simple ECU that controls the Cummins R2.8 Turbo Diesel engine and turns on the Flex-a-lite electric fan, everything is driver-operated. And that includes deciding in which gear the UACJ-6D moves.

    But his insanity goes beyond simply eschewing an automatic transmission for a manual. Nope, he’s gotta have a gear for each and every occasion—no exaggeration. The drivetrain he chose to mount behind the 161hp, 267–lb-ft turbodiesel was, um, varied, to say the least. For starters, in order to mate the Cummins-specific bellhousing to a 4x4 transmission, Axis Industries got the nod. The company has come up with a super-nice billet adapter system that mates the Cummins bellhousing to your choice of AMC AW4 auto, AX15, NSG370, or NV3550 as well as Chevy 4L60E, 4L80E, and 6L80E transmissions. The adapter system retains the Cummins flywheel in addition to the flywheel or flexplate of the donor transmission. The starter engages the Cummins flywheel, and the clutch or flexplate handles the engine-to-transmission coupling. By the time you read this, Axis should have its Chrysler 8HP70 adapter kits ready as well. But when we were working on the UACJ-6D, Axis only had the AMC components ready.

    We sent our factory Cummins flywheel to Axis to be lightened from its roughly 30 pounds to 15 pounds and grabbed a stock-spec, neutral-balanced 1995 Jeep 4.0L flywheel from a local auto parts store. A super high-quality South Bend Cluth pressure plate and disc ride the Jeep flywheel. We nabbed a new AMC bellhousing from Advance Adapters and then ordered a Ranger Torque Splitter with a 27 percent overdrive built with AMC front and Chevy rear transmission patterns. Advance can build the Ranger with several different bellhousing patterns from AMC/Ford, Toyota, and large- or small-bearing retainer GM. Hazel has used the Ranger in other projects and knew from experience how well the units work.

    Behind the Ranger is a dead-stock SM420 that Hazel purchased for $100 without even cracking the top for inspection. It was then fitted with an Advance Adapters Dana 300 1x23 spline conversion stub shaft and adapter before getting mated to the Offroad Design Magnum Box and a Ford NP205 T-case, which we covered in depth in the story “NP205 Gearing Options From Offroad Design” (goo.gl/yx8eBP).

    The resulting flexibility is staggering. Need to go super-crazy, slinky-slow? Drop the SM420 into its 7:05:1 First, engage the Offroad Design Magnum Box’s 2.72:1 Low, and put the Ford NP205 in 1.96:1 Low for (factoring in the 4.88 axle gears) a combined crawl ratio of 183:1. That’s slow enough to watch paint dry while you drive. But if it’s ever just too slow, Hazel can engage the Advance Adapters Ranger Torque Splitter overdrive to kick that down 27 percent, giving him a 134:1 Low. Or, use the Ranger to split the SM420 gears on the street, effectively turning the four-speed SM420 into an eight-speed multi-ratio transmission with a 0:73:1 Overdrive. Yes, you can engage any of these gearboxes in any combination in either two- or four-wheel drive. Enjoy the five-shifter drivetrain assembly, and next time we’ll show you how we mounted and plumbed the Cummins R2.8 Turbo Diesel.

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