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2009 Jeep Wrangler JK X - JK Prerunner

Right Front Angle
Phil Howell | Writer
Posted December 1, 2010

Fast Fun

As you might have noticed from reading, we're fascinated with trail vehicles that can not only handle tough trails and obstacles, but can travel at high speed on graded dirt roads, over whoops, etc. Our Trailrunner JK is one of these. Curt Hildebrand's JK Prerunner raises the bar. We've never driven a JK that can go so fast in the dirt.

Curt is the R&D engineer for Teraflex. He likes to rock crawl, but also loves to go fast. He knew that by mainly using off-the-shelf parts from Teraflex he could build a clean, simple JK that would be impressive.

Curt started with a basic X model JK two-door. It has the 3.8L V-6, NSG360 six-speed manual tranny, NVG241 transfer case, Dana 44 rear end, and Dana 30 front end. A set of 5.13 gears were installed, as was an Eaton Detroit Locker in back. The front 30 housing was trussed, but all bracketry (except lower shock mounts that were moved outward) remained stock.

The suspension shines. For needed up travel, the upward-bent lower arms were replaced by Teraflex straight arms. Teraflex 3-inch front and 2.5-inch rear coils gave the needed lift and are the perfect rate for this application. Teraflex 4-inch Speed Bumps were installed in the stock front location and 4-inch rears were frenched into the frame. Bilstein 7112SB shocks were valved after Curt and Shane Casad from Bilstein met him in the desert for a valving session. They worked.

Stock Rubicon wheels were used with no spacers, as Curt didn't want the scrub radius affected by wheels with less backspacing. This is fine in theory, but the LT285/70R17 Goodyear DuraTrac tires rubbed on the frame and other components. A new JK Trailrunner uses OE wheels with a small spacer.

The JK Prerunner has 12 inches of suspension travel. It crawls fine, but really shows its stuff speeding over whoops and dirt roads. As we drove the JK, Curt would yell, "Don't slow down!" as we approached big whoops. So, we didn't slow down and slammed into them. At 50 mph. To our surprise, the JK was controlled, didn't launch the rear, bottom the front, or do anything strange. It soaked up the bumps and kept going. It would go as fast as we wanted on graded roads.

Curt's JK shows what can be done (and what a JK is capable of) with a few quality parts and leaving the rest of the Jeep stock. It's fast and fun.

SPECIFICATIONS

Vehicle: 2009 Jeep Wrangler JK X
Owner: Curt Hildebrand
Engine: 3.8L V-6
Induction: MPFI
Transmission: NSG370 six-speed manual
Transfer Case/Low Range Ratio: NVG241/2.72:1
Front End: Dana 30
Rear End: Dana 44
Ring And Pinion: 5.13:1
Front Differential: Open
Rear Differential: Eaton Detroit Locker
Suspension: Custom Teraflex long arm, Bilstein shocks
Tires: LT285/70R17 Goodyear DuraTrac
Wheels/Backspacing: 17x7.5 OE Rubicon/6 inches

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