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55,000 Mile Jeep Wrangler Rubicon JK - 55KJK

Posted in Project Vehicles on November 1, 2009
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We were likely less than 100 miles away from catastrophic failure.

Wouldn't it be nice if you could road test a new car to death before actually buying one? Well, that's kinda what we've done for you here. Our project JK may be less than 3 years old but we've logged over 55,000 on- and off-road miles. And not only that, we've modified it in realistic ways that you would modify your very own Jeep. In "Ready-To-Run Part II" (May '08) we left off with nearly 21,000 miles on our '07 Wrangler Rubicon. Since then the Jeep has been on several 1,000-mile-plus road trips, it's been over the Rubicon Trail, all over Moab, Utah, and through many local trails, mud pits, water crossings, snow drifts, sand dunes and so on. You could say we know our Jeep pretty well. So how has it held up and what mods has our Jeep rejected? Read on.

Mile 28,620
A trip to the Pismo Dunes in California once again confirms the lack of power in 4-Hi and that the 4:1 is too low for sand use. Why can't we have a factory three-speed transfer case? Dune bashing nets us an actual 7.7 mpg for fuel economy. So no power and the fuel consumption of a small-block V-8 in the dunes. It's impressive that it's even possible.

Mile 29,336
A road trip resulted in an actual 20.5 mpg! Not bad for a Jeep Wrangler on stock mud tires. Two things we've noticed that improve mpg are frequent oil changes (every 3,000-5,000 miles, depending on how much dirt you see) and keeping the engine rpm below 2,250 rpm on the highway. Changing out dirty oil has netted us as much as a 2-mpg improvement. The mpg gauge in our Jeep is still inaccurate by about 1-2 mpg so check your mileage manually at the pump.

Mile 30,579
Our rear locker problem was eventually solved by simply replacing the entire rear axle assembly. Both front and rear lockers work again.

Mile 33,757
We bolted on our 4-inch Black Diamond suspension kit. It went on fairly trouble free in our garage with hand tools. We used a Pro Comp Accu Pro calibration tool to match the speedometer to the new 35-inch tires. For the full install and driving impressions check out "Home Schooled" (Nov. '08).

Mile 34,604
We get the best on-road wear from our 35x12.50R17 BFG KM2 tires mounted to 17x8.5 AEV wheels with 25 psi all around. Off-road we'll drop 'em into the low teens and even single digits in the sand thanks to the beadlocks.

Mile 34,707
We've come to the realization that the addition of a 4-inch lift and 35-inch mud tires has cost us about 1 mpg in fuel economy. And the hood buffets because the Jeep is no longer nose-down. No biggie. We'll live. At least it looks cooler and goes further up the trail.

Mile 35,515
We installed Poly Performance skid-plates. Pretty slick setup. Check out "Flat Bottom Baby" (Nov. '08) for more info.

Mile 37,658
We started smelling burnt grease and heard a new whirring noise. It turned out that the short factory rear CV driveshaft of our two-door Wrangler couldn't handle the 4-inch lift. The CV boot tore and all the grease spit out onto the exhaust. We were likely less than 100 miles away from catastrophic failure. So we unbolted the driveshaft, shifted the transfer case into 4-Hi and drove home 120 miles in front-wheel-drive.

Mile 37,778
We installed a bolt-in J.E. Reel U-jointed driveshaft out back along with some Rubicon Express adjustable upper control arms to adjust the pinion angle. The very next day we hit the road for the Rubicon trail. We decided to keep the stock front CV driveshaft in place to see how long it would last with the lift. So far so good.

Mile 38,455
With the Rubicon swaybar electronically disconnected, the driver side suspension somehow overextended on the trail and then compressed. This caused a swaybar link to bend. No biggie. We simply unbolted the link, hammered it straight, and bolted it back in again. The problem has not reoccurred since.

Mile 38,600
There is a slight exhaust leak on cold starts. We couldn't find where it was coming from but it looks like the exhaust downpipe occasionally rubs on the Poly Performance skidplate. The stock motor mounts allow a lot of movement.

Mile 40,118
We don't see any need to swap out the 4.10 gears with 35-inch tires and our manual transmission. It works perfect, especially for the higher freeway speeds we typically encounter in Southern California. The 35s and 4.10s aren't that bad on hills either. We can generally hold Fifth and rarely need to get down to Fourth gear.

Mile 43,775
The BFG Mud Terrain KM2s don't work so hot on snow and ice. A "quick" snow run in the mountains went horribly wrong. We ended up getting stuck. We rocked the Jeep back and forth with Forward and Reverse gears. Shifting the T-case in and out of 4-Hi and 4-Lo repeatedly with the locker lights blinking resulted in the front locker sticking on. Eventually we drove out of it and had to limp home with the front locker stuck on like a spool. About 60 miles later the additional load caused the power steering pump to fail. We removed the diff cover to inspect the locker and found that it would no longer disengage on its own. We had to help it with a pry bar. So we pried it unlocked, unplugged the front locker wire and replaced the power steering pump with a new one. Our front locker is out of warranty and dead to us, for now.

Mile 48,411
We started to notice some wobble in the steering wheel. The tie rod looks a little bent from hitting trail debris so we may need to adjust the toe-in.

Mile 49,081
We rotated the tires for the first time in over 15,000 miles. They are wearing very well and still have over 3/4 of the tread left, but they are a little noisier than when new. It's got to be expected with mud tires, but not a bad experience considering we never even balanced them. The AEV beadlocks are still holding up excellent. However, the glue on the yellow center-cap stickers has long since melted (during hot summers) and allowed the stickers to fling off somewhere along the road.

Mile 53,258
Our JK loves to wander slightly in deep road grooves and the steering wheel wobbles a bit over rough surfaces. We still haven't checked the toe-in. We'll have to get to that soon. We're told 1/8-inch toe out can cure these issues.

Mile 55,500
The exhaust leak is getting a little worse. Good news is it might be easier to find now. The factory front CV driveshaft is a little battered from rocks but it's holding up fine after running with the lift for over 20,000 miles. Like many JKs with 35-inch or bigger tires, our front axle housing is a little bent. It still functions fine but we'll be addressing that along with fixing the front locker soon.


Pro Comp Suspensions, Inc.
Chula Vista, CA 91914
Poly Performance
San Luis Obispo, CA 93401
Rubicon Express
Rancho Cordova, CA 95742
Royal Oak, MI 48067

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