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1988 Jeep Wrangler YJ Colorado rock crawler

Posted in Features on December 21, 2016
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Sergio Martinez’ Jeep YJ is not a show ’n’ shine winner, but it takes the trophy every time it hits the trail. “I have always loved four-wheeling and how capable a Jeep is off-road,” Sergio says. His interest in four-wheeling started growing up in Texas driving around the sand dunes. In 2000, he moved to Colorado where he met the original owner of this YJ. “I bugged him almost every day trying to get him to sell it to me. One day I told him, ‘I have $4K cash,’ and finally, he agreed.” As time went on, Sergio became more interested in rockcrawling, having tackled most of the tame trails in Colorado.

After blowing up the 9-inch rearend for the third time, the search for something beefier was on. For two years, it sat while parts were stockpiled. After finding a 14-bolt rear axle out of a ’85 Chevy G30 van and a Dana 60 out of ’97 F-350 for the front, it was game on. Five years later, he has an amazingly capable crawler. Both axles house 5.13 Yukon gears and Detroit lockers. The front is also equipped with Yukon 4340 axleshafts. He left the stock Ford disc brakes on the front axle and did a disc conversion on the rear. Driveline Specialties built custom long-travel driveshafts for him.

The suspension is an interesting set up. He moved the axles a bit to create a 108-inch wheelbase. A custom 4-link front and rear suspension built using Summit Machine aluminum links, 5⁄8-inch Heim joints with 3⁄4-inch shanks, and 35-inch limiting straps from OnTrack Performance, locates the axles. The front sports 2.0 King 14-inch coilover shocks, and the rear uses stock TJ front coils set in Ballistic Fab universal coil buckets that Sergio modified to fit. Rancho shocks also grace the rear. A 1-inch body lift was added after the engine and transmission upgrade, as the transmission was hitting the tunnel.

The powerplant is what first made us do a double-take on this Jeep. As soon as he fires it up, you can tell there is more to it than meets the eye. The 6.0L V-8 and cold-air intake are from an ’05 Chevy 2500. The bottom end is stock. However, a Comp cam and LS7 lifters and valve springs were installed, and the heads were decked 0.030 inches by Colorado Custom Cylinder Heads to bump the compression ratio to 10.5:1. An LS Muscle oil pan, BBK 1 3/4-inch headers, a JEGS center turndown 2 1/4- to 3-inch exhaust, and Flowmaster muffler round out the engine mods. A GenRight Crawler fuel tank carries enough gas for long trips. A 4L60E automatic transmission backs the engine. A ’97 Chevy 1500 donated the NP241 transfer case with a low range ratio of 2.72, and Sergio designed and fabricated the custom T-case shifter.

Like we said, Sergio’s ’88 Jeep YJ Wrangler is no show ’n’ shine mall crawler, but if you ever see it crawl a rocky trail, you will be more than happy to give “Best in Show.” We thought you would like it.

A beefed up 6.0L V-8 tucks nicely under the hood. The Comp cam and bumped-up compression ratio help achieve that extra horsepower needed when climbing over obstacles. He’s not afraid to use the skinny pedal when a situation calls for a little more power.
The interior is basic with no frills. Beige PRP buckets, G-Force harnesses, and Auto Meter Phantom gauges are about it. Sergio built his own custom rollcage out of 1.75-inch, 0.120-wall DOM tubing and 1/4-inch plate. He used B-pillars from Poison Spyder Customs for the cage base.
Sergio isn’t afraid of a little rock rash on his Wrangler. The only exterior additions are Genuine Steel bumpers front and rear and Poison Spyder Comp Corners. A Contico Xtreme Tuff locking box for recovery gear is mounted on the back instead of a spare tire.
Custom skidplates made out of 1/4-inch plate steel, with 1/2-inch-thick UHMW polyethylene sheets for protection and extra slide-ability. A custom cross member supports the 4L60E transmission. Sergio rebuilt the trans himself, adding in a Corvette shift kit and servos, a TransGO spacer plate, and a Lokar shifter.
Up front, you’ll find a Ford Dana 60 front axle, 5.13 gears, a Detroit locker, and 2.0 King 14-inch coilovers. A hull hydro PSC steering system helps this beast navigate its way through the rocks. Signature lime-green 8620 chromoly steel Crane diff covers add additional protection for hardcore crawling.
A 14-bolt GM rearend with a disc brake conversion, 5.13 gears, and a Detroit locker can be seen under the tail of the YJ. Summit Machine aluminum links, stock TJ front springs in customized Ballistic Fab universal coil buckets, and Rancho shocks make up the rear suspension.
A Smittybilt X20 10,000-pound capacity winch mounted on a Genuine Steel front bumper sits on the YJ’s nose. Contact with the terrain comes in the way of 39.50x13.50R17 Interco IROK’s mounted on Pro Comp Rock Crawler 152 wheels with DIY weld-on beadlocks.

Hard Facts:

Vehicle: ’88 Jeep Wrangler YJ
Engine: 6.0L Chevrolet V-8
Transmission: 4L60E
Transfer Case: NP241
Axles: (front) Dana 60, 5.13 gears, Detroit locker, Yukon 4340 chromoly ’shafts; (rear) GM 14 bolt, 5.13 gears, Detroit locker, Yukon 4340 chromoly ’shafts.
Suspension: Custom 4-link with 2.0 King 14-inch travel shocks and Currie Antirock (front); custom 4-link with Rancho shocks and stock TJ front coils in modified Ballistic Fab buckets (rear).
Tires: 39.50x13.50R17 Interco IROK
Wheels: Pro Comp Rock Crawler 152 wheels with DIY weld-on beadlocks.
Steering: Full hydro PSC steering system
Built For: Extreme rockcrawling

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