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2007 Jeep JK Wrangler

Posted in Project Vehicles on April 1, 2006
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Contributors: Courtesy of JeepRick Péwé
Photographers: Courtesy of Jeep

You knew it would happen, and you knew it would be this year. What you had also hoped for is that Jeep didn't ruin the new Wrangler (designated internally as JK) or undermine any of its off-road ability and heritage. Luckily for you and us, the new Jeep has its soul firmly in the past, while still looking toward the future. We haven't had a chance to drive it yet, but we got this exclusive deep dive into the mechanics and design of the JK, just so you'd be prepped when the first models roll off the assembly line this fall. Sure, we'll give you driving updates when they're available, but the secret hot smoke and dope is here now for us to share with you. Bottom line: The new Jeep Wrangler is bigger and beefier, with many upgraded components which should make it even a better wheeler, and a much better road machine. Check it out.

First off: It still looks like a Jeep. Since first impressions are usually the ones that stick, the Jeep design crew knew to keep the round headlights, seven-slot grille, trapezoidal wheel arches, and open body configuration, along with a fold-down windshield. Of course in the ever-increasing quest for better fuel economy and pedestrian safety, the grille has been laid back and the windshield is now slightly curved. We'd rather pay more for fuel and whack a few pedestrians off the trail, but hey, overall the look ain't bad. It's full-on what the Jeep Gladiator concept looked like when revealed at the 2005 Detroit Auto Show, with big external door hinges and a sloped-back grille. In addition, the big flexible fenders are designed to cover the tread, but be removable for customization. Other design cues from many a show vehicle including the Jeep Rescue have made their way onto the new JK as well, with more exciting revelations yet to come. But looks aren't everything, and compared to the current TJ Wrangler, the JK is 5 inches wider with only a 3 1/2-inch-wider track, and 5 1/2 inches longer with a 2-inch longer wheelbase (95.4 inches) for this two-door, so it still looks proportional in a Jeep sort of way. Somehow this increase in overall heft (about 300 pounds) still allows for a 44.3 degree approach angle, 25.4 degree breakover angle, and a 40.4 departure angle on the new Rubicon Wrangler, which, through a combination of taller tires and moving the gas tank forward, rivals today's Rubicon Wrangler at 49, 25.4, and 33.9! And finally, what can you say about the blow-molded bumpers, other than they're flexible and removable? 'Nuff said!

Mechanically, the biggest news is the 3.8L V-6 engine replacing the venerable 4.0L straight six, a holdover from some 35 years ago. While strong, torquey, and reliable, the old 4.0L couldn't meet current or future smog rules, weighs much more than the V-6 replacing it, and makes designing frontal impact parameters very difficult. Our biggest concern will be the torque band of the engine, previously used in the Pacifica and Caravan. The old 4.0L develops 190 hp at 4,600 rpm and 235 lb-ft at 3,200, while the V-6 gives 205 hp at 5,200 and 240 lb-ft at 4,000. This means you get a higher revving engine that won't match the low-end torque of the inline six, so some sort of gearing compromises will have to be made. No more engine lugging like a tractor with your Jeep, but spinning the tires in the sand and mud will be much more fun! But gone too is the mechanical throttle cable, as this new generation is a drive-by-wire, allowing a multitude of safety and engine management functions to be applied. And if you're looking for a four-cylinder, don't bother, unless you go overseas where a diesel 2.8L VM is available, even though they would sell like hotcakes here.

Another major change is the 32-inch BFGoodrichs instead of Goodyears on the Rubicon model. While they are still load range E with too much air in them for our uses, the BFGs provide better wet weather traction and quieter operation in this application. They are available in the 17-inch size, while the Wrangler X and Sahara get 16-inch Goodyears, and the Sahara has the option of Bridgestones on hideous 18s. We just hope we don't see any of those, or have to test them. And in case you didn't notice, the wheel pattern has increased on all Wranglers to a 5-on-5-inch bolt circle. Someday, they may get back to the 5-on-5 1/2 like they should!

Major internal changes are extremely important and are buried in the axles. The Wrangler X and Sahara get a Dana 30 front and a Dana 35 rear, and the optional towing package nets you a rear Dana 44 as well. A Trac-Lok limited slip is optional on the 35 and 44, with 3.21 and 4.10 gear ratios available. The 35 is now a non-C-clip captive bearing style, with stronger shafts, strengthened tubes, and bigger pinion bearings and pinion. The front 30 has bigger pinion and pinion bearings and bigger axle joints and stub shafts, and also features a captive unit bearing so the stub axle can be removed if needed. And since bigger is better, the Rubicon's 44 front is now a reverse-pinion design, has stronger tubes, a bigger pinion shaft and bearings, bigger 1350 series U-joints, better axles, and a captive unit bearing. The Rubicon's rear 44 features bigger pinion bearings and pinion, a larger (yes, larger) ring gear by 10 mm, bigger tubes, and (gasp) 32-spline 1.4-inch-diameter special axleshafts. That stuff will keep the aftermarket busy for a while, and, oh yeah, the completely new-style lockers front and rear are now engaged magnetically, instead of vacuum operated. Less is better in this case. Did we mention the drain plugs? Find that in another vehicle....

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Standard carryover transmissions prevail here with the NSG370 manual six-speed and the 42RLE four-speed auto. The auto gets 4.10 axle gears, while the stick can be had with 4.10 or 3.21 gears. These trannies worked fine before, so there wasn't much sense changing them. But the "next generation Command-Trac" is better and, yes, bigger. The NVG241 with 2.72:1 low range and the Rubicon counterpart the NVG241OR Rock-Trac with 4.0:1 low range both get upgraded with a cable shifter instead of linkage, and 18 bolts holding the case halves together instead of 9. The increased stiffness makes for better sealing and durability, and they also feature fixed yokes instead of the slip-shaft stuff. But on the ends of the yokes are big, beefy CV joints ( the real Rzeppa style, not a double cardan), for increased strength, smoother operation, and more angularity. We aren't sure of the durability of boots and such, but again the aftermarket will have a heyday.

The suspension remains basically the same as the TJ with the five-link coil suspension, but all of the arms are longer and, yes, bigger and better. Box construction instead of U-channel arms helps the big bushings to move, yet stay stable. Massive track bars are nearly parallel, and the brackets are highly upgraded as well. The coil rate is said to be softer than before, but matched to the low-pressure twin-tubed shocked X, and high-pressure monotube shocks for the Sahara and Rubicon. Better yet, the Rubicon gets the electronic disconnecting front stabilizing bar as used on the Dodge Power Wagon. Known as the Active Sway Bar System (ASBS), this goodie unhooks in low range under 15 mph to increase articulation by about 28 percent in the rough. The frame is as big as some truck frames, and is 100 percent stiffer in bending, and 50 percent stiffer torsionally. Hydroformed crush rails in the front add occupant and target safety and ease of repair, should it be needed. Steering geometry is far better now as the floppy center steering design is gone, replaced with a conventional cross-over system to eliminate bumpsteer, head toss, and sloppy feelings. A special high-steer right knuckle, bigger and better tie rods and steering arm, and a refined recirculating-ball power-steering box all help fight old-fashioned steering systems for a precise feel, sort of like what we would build ourselves. The scrub radius is also vastly improved from 50 to 14 mm, which can make a big difference in steering feel. Brakes gain improvements too, with four-wheel disc only (drums are gone) with bigger and better rotors and calipers, and of course the obligatory alphabet soup of traction and safety controls.

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And speaking about alphabet soup safety, here's the list. What's really good is that the functions are modified when in low range, for the better. Starting with the traditional ABS (antilock braking system), the calibration is changed in low range for less sensitivity and more actual lockup. TCS (traction control system) uses brakes to limit spin while pulling power and BA (brake assist) simply senses a full panic stop and gives added pressure to the brakes-more than your foot ever could. But the big news is the ESP (electronic stability program) and the ERM (electronic roll mitigation) system. The cool thing is that ESP has three modes: full on, partial off, and full off. The ESP senses the amount and speed of yaw, pitch, and roll, then pulls engine power or selectively applies individual brakes to keep you on the road, and affects the ERM, ABS, and TCS. In partial off mode, the TCS is off, and less ESP is used. In full off, TCS, ESP, and ERM are off completely. But in low range, ESP on gives you ABS lessened, TCS engine management off, and brake traction off, but BLD (brake lock differentials) gets a different calibration, and ERM remains on. With the ESP off in low range, the same scenarios are in effect, but the ERM is off. Any questions?

Inside the new cockpit there's a generous increase in space, with 4-5 inches more hip and shoulder room and a couple inches down by the feet as well. The cargo area has hidden storage and room unmatched in the previous Wrangler. The dash features only speed, tach, temperature, and fuel gauges, while the centerstack houses all the regular HVAC controls, plus a nav screen and MP3 capability with Sirius radio. New seats and fabric designs with special Yes repellent fabric might be cool, and they complement the carpet which is still removable for hosing out the innards. Even though the floor is layered with a special closed-cell sound-deadening foam-the floor drain holes remain. When designers and marketing people describe interiors as athletic, you know they have little grasp of the English language. But lo and behold they got it right this time, as the driver seat actually moves up and down manually for an unparalleled view of the road, sort of like a gymnast. We'll give 'em that one.

The new hardtop is a big deal for Jeep, which is a three-piece modular style. The removable left and right panels can be taken off and stored in the back, and the whole top is light enough for two people to remove. The standard Sunrider soft top, which can be left half open for an airy feel, is still available, and doors are either full or half and completely removable.

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