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Beyond Rubicon: The Mopar "Trail Boss" Jeep Wrangler JK

Posted in Features on February 15, 2011
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Don’t just throw money at your favorite mechanic and tell him to make it even better! Some very astute Mopar engineers who are also Jeep enthusiasts have already done that. After spending many hours on the trails and many days in front of their computers, these engineers have come up with some truly awesome new stuff for your Rubicon. Adding these factory-warranted parts to your JK Rubicon (new or used) will make it an even better, more trail-worthy Jeep.

Our lunch stop was the Moss Mansion, a two-story concrete house that was one of the first (if not the very first) poured-concrete structures in Arizona. The Walapai 4WD Club has adopted the trail and the mansion, and they keep the trail free of debris and the mansion free of graffiti.

While it may not be ready to compete in the King of the Hammers race, what street-wise Jeep is? When it’s done, the Trail Boss (a nickname given to this Moparized Jeep to make it easier to talk about) rolls out the dealer’s door ready to tackle any trail this writer has ever seen in nearly 50 years of ’wheeling. That’s almost half a century of exploring such places as the Everglades, Moab, the San Juan Mountains of Colorado, Lucerne Valley of Southern California, and the Sierra Nevada (Rubicon and Dusy Ershim).

We guess if we follow the reasoning behind naming the Rubicon (arguably up to now the best all-around Jeep to ever roll off an assembly line), we could have named it The Dusy, but that name was already taken by a famous car long before this vehicle came about.

Speaking of the Rubicon, it has to be the basis for the Trail Boss because of its heavier-duty driveline components. The lighter-weight axles and transfer case of the other JK models would not be able to accept the Trail Boss’s lower gears and taller tires and still be economically feasible warranty-wise.

Moss Wash trail is a 3+ in spots; spots such as this one, because it closely follows the creek bed where the dirt and sand is regularly washed out from between the large boulders. The 4.88 gears and 4:1 low range allowed the Trail Boss to creep over boulders.

Let’s just see what the Rubicon option group brings to the trailhead. As with all JK Wrangler models, it is powered by a 3.8L V-6 sequential multi-port injection engine, which has 202 horsepower at 5,000 rpm and 237 lb-ft of torque at 4,000 rpm. Power is supplied to the Dana 44 axles through either a six-speed manual transmission or a four-speed automatic tranny, which is bolted to the Rubicon’s Rock-Trac part-time 4WD transfer case with a 4:1 low range gear ratio. Electronic-locking front and rear differentials, a Rubicon exclusive, lock the left and right wheels together to maintain the forward momentum for the ultimate in Wrangler traction. The instrument panel-mounted rocker switch can lock the rear, the front, or both axles. Also exclusive on the Rubicon (and part of its performance suspension), you’ll find an electronic front sway bar disconnect. With the flip of a switch, the front sway bar is disengaged when driving less than 18 mph in four-wheel-drive low range. This allows the wheels to drop and compress up to an additional 20 percent for improved front wheel articulation.

We were going to mention the stock Rubicon 17-Inch aluminum wheels and BF Goodrich LT255/75R17 BSW off-road tires with matching spare, but the Trail Boss is equipped with larger tires and military-grade beadlock wheels so there’s really no reason to go into the Rubicon’s OEM tires and wheels. Suffice it to say that in our opinion, while the larger tires and stronger wheels add greatly to the overall traction and trail worthiness of the Trail Boss, Rubicon OEM wheels and tires are sufficient until the tires wear out.

We’ve listed the additional products that have been added to this Rubicon to make it the Trail Boss. Check out the photos and captions where we’ve explained each item more thoroughly for your consideration. One other thing we want to mention at this time; don’t think that you have to buy a new Rubicon in order to enjoy these improvements. If you already own a JK Rubicon (2007 to 2011) or are considering buying one, you can order these products at your local dealer and still enjoy the warranty that came with your Jeep. Plus, there is no Trail Boss accessory package, which means that you can order the products one item at a time (a la carte) or in selected groups.

Looking more like a club logo than a manufacturer’s decal, the stylized Mopar decal tells everyone that this is a special model Jeep.

While you’re reading over the following list, remember that unless otherwise noted the listed prices are per item. Installation labor, shipping (if any), or multiple items are not included.

A 2-inch lift was needed for the larger, more aggressive 34-inch Goodyear MT/R tires.

The new Jeep dealer-offered Mopar JK parts include: Mopar off-road bumpers, front ($612) and rear ($558); front skid plate ($254); Warn 9500 XP winch ($1,349); AEV rear corner guards ($402/pair); taillight guards ($132/set); fuel door ($111); rock rails ($572/set); windshield-mounted Hella off-road lights ($125/pair) and mounts ($103/pair); cold air intake ($359); 2-inch lift kit ($1,510); rear differential protective cover ($79); Mopar military-grade wheel ($662); Goodyear 34-inch MT/R tire (price varies); 1-1/2-inch wheel spacers (price varies); and 4.88:1 differential gears (price varies).

There are other miscellaneous accessories on the Trail Boss, such as seat covers, mats, etc., but they’re not included here. The total for the Trail Boss package as you see it in the photos, including the installation charges, is $11,598. (All the items are also available for the JK Unlimited four-door Rubicon.)

That is a lot of money, especially on top of the Rubicon’s window sticker price of $30,350, but remember that it all comes with the Jeep’s original factory limited lifetime warranty. If a locker quits, the tranny starts slipping, or a U-joint gives up, just take the Jeep to the nearest dealership.

Since the Trail Boss was outfitted with a 2-inch lift and 34-inch Goodyear MT/R tires, I decided the Moss Wash trail would be a difficult test for it. As rocky as the trail was, it wasn’t really a test after all—the Trail Boss took it all in stride and with highway air pressure in the tires, too.

The Wrangler’s window sticker says the Trail Boss ought to get 15 mpg around town and 19 mpg on the freeway, but the added weight of the Trail Boss’s accessoriesnot to mention its taller tires and lower gearsputs an eraser to those figures. But who buys a Jeep for its mileage? The better it performs off road, the lower its miles per gallon are going to be. Hitting the freeway at 75 to 80 mph also pulls the mileage down, as does hitting the trails in low range, so our two tanks averaged 12.4 and 10.7 mpg, respectively.

Not too shabby, in our opinion, for a Jeep twisting 4.88:1 gears, heavy beadlock wheels, and 34-inch tires. We’re sure slowing down to 55 mph on the freeways, and reducing the fun quotient with a lighter right foot while driving to the bookstore or Staples, would vastly increase the Trail Boss’s mileage, but it wouldn’t be as much fun zipping around in a lidless Jeep.

Due to the lead time needed for the magazine, by the time you read this there could very well be many more Mopar aftermarket products available, such as 4.56 gears, additional engine gauges, etc. Check with your local Jeep dealer or for an up-to-date list.

Having a ’07 Rubicon Unlimited as a daily driver for 3.5 years, the Trail Boss’s nimbleness was a pleasant surprise.

Additionally, we all know that when a vehicle’s differential gear sets and/or tire size is changed, the vehicle’s speedometer reading is changed. With the Wrangler, this means modifying the onboard computer to give a correct speed and mileage record. Jeep dealers cannot correct the computer for tires larger than the 32-inch Rubicon OEM tires, so you’ll have to go to the aftermarket. I recommend the American Expedition Vehicles re-calibration tool; it’s called Pro Cal.

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Auburn Hills, MI 48321

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