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March 2012 Your Jeep Tech Questions

Posted in How To on March 1, 2012
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Who You?
Dear Verne, who the hell are you?
Via email

Well Bob, my name is Verne Simons. I grew up in North Carolina and now live in Arizona. Some of you may recognize my name from freelance articles that have been splattered throughout Jp magazine over the past eight years or so. Before that, I worked for two years as then brand-new Jp Editor John Cappa’s sole feature editor. Editor Hazel, whom I have known since I first started working at the magazine way back in 2000, recently asked me to write the Your Jeep column on a regular basis. I am totally stoked to be involved in the magazine on a regular basis again! Basically I am a Jeep nut who is also a total nerd.

My first car was an ’83 CJ-7 that was handed down through my family. It looked great (chicks dug it!), but the factory carb made it basically undrivable most of the time. Since then, I have owned two TJs, three XJs, a YJ, a WJ, a ’49 CJ-3A that you might recognize, and I have been building a ’56 CJ-5 from the ground-up, which is being covered right here in the pages of Jp. I love traveling, photography, cooking, eating, animals, BBQing, eating BBQ’d animals, mountain biking, RC crawlers, being outside, camping, wrenching, and wheeling. I am a cheap bastard who would usually rather learn how to do something myself than pay someone else to do it for me. I have also spent time as a paleontologist, traveled all over the world, taught college classes in Ohio, and now work as a part-time alligator wrassler. Yeah, seriously. Now Bob, who the hell are you?

Rubi or Regu
I have a really nice ’07 two-door JK Rubicon with a 4-inch Teraflex long-arm lift and 35-inch tires. My wife and I have enjoyed wheeling in Arizona and the southwest, including the Rubicon Trail. The vehicle goes pretty much anywhere I point it. My problem is space. We enjoy camping more than anything and it’s always a challenge to get all the camping gear, clothes, recovery gear, kitchen sink, and so on, packed into the little Wrangler. In fact, it’s nearly impossible to get everything we need for a week or more in the back country. To handle the overflow, I have a Body Armor roof rack and basket that won’t fit in the garage, so I have to remove the basket after each trip. I thought of digging out the slab in the garage to give more vertical height. I thought of getting a trailer for tent and gear. I thought of getting a Yakima cargo carrier to get another 15 cubic-feet of space. Finally I thought of simply getting a four-door Wrangler.

I’m struggling with the decision of getting a Rubicon or a Sport. Thanks for the recent article “Rubicon vs. Regular” in the May ’11 issue. I really love the 4:1 low range of the NV241OR T-case, and I like the electric lockers (although I hate the placement and operation of the locker switch). I’m not crazy about the inherent weakness of the front axle, although I have had no problems so far. And I don’t like the lift. The 4-inch lift makes it hard for old bodies to get in and out of the Jeep; so much so that my wife tore her shoulder cartilage and has to undergo surgery this month.

I am hoping to put 35s on the new vehicle with no lift (or a small spacer lift). If I go with the Sport, I am particularly concerned about the 2.72:1 transfer case (not sure of the model). I would replace the Dana 30 front axle with a Dana 44. I would add selectable lockers (thinking of ARB air lockers, but where would I put the compressor?). I would also like to replace the T-case with the Rubicon model or equivalent. Hopefully all these mods will cost less than the extra I would pay for the Rubicon, and would be better suited to the type of wheeling I like to do. Can you help me with my decision? Particularly, what’s involved with the transfer case swap, and where would I get one?
Rob Hewitt
Phoenix, AZ

The ’12 models have the improved 3.6L Pentastar V-6, however the auto transmission is the five-speed WA580 currently used in the 5.7L-equipped Grand Cherokee and Dodge vehicles. Advance Adapters has yet to determine if it will have a Rubi-Crawler available for that transmission/T-case combo. Otherwise, I’d say the no-brainer would be to get a 3.6L/auto-equipped Sport and add the Rubi-Crawler to have your choice of 2.72:1 or 5.44:1 low range.

As for your front axle, I’d suggest a Dynatrac ProRock 44. To save a bit of money, you could buy the axle from the ball joints-inward and reuse your Dana 30 knuckles and brake assemblies. They’re the same parts as the Dana 44. I would strongly suggest checking the option box for Dynatrac’s ProSteer ball joints since the factory units wear quickly.

For the locker, Dynatrac will tell you the ARB Air Locker is the strongest, but I’ve really liked the Eaton E-Lockers I have in my Wrangler. They’ve proven durable for me and there are no air lines to run. Just an electric rocker switch that you can have mounted wherever you like. If you do go ARB, you can probably squeeze a compressor under the rear of the floor (basically under the rear seat area).

To run 35s, check out the Daystar “Comfort Ride” combo kit, PN KJ09154BK. It includes 1¾-inch suspension spacers and a 1-inch body lift that will give you enough clearance for the 35s you want to run. You’ll retain the factory springs for a comfortable ride and it is low enough that the suspension and steering geometry won’t be impacted.

Marine Mileage
I’m a United States Marine currently station in Afghanistan. I have a four-door ’95 Jeep Cherokee with the 4.0L six-cylinder. I will be getting home in the next few months and would like to start making improvements to my Jeep. I know you have been over this several times in your magazines, but I need help. I would like to know the best step up to improve the fuel economy. At this time the Jeep has no performance modifications, so I will be starting with a 100-percent stock Jeep. Any info on this topic would be put to good use once I get home.
Gordon Morse
Richlands, NC

If your primary concern is increased mileage you’re going to want to leave the suspension and tire size stock. Raising the body creates more air turbulence under the vehicle, which hurts economy. It’s a bit like running down the road with a small parachute deployed behind the vehicle. Here are the things I’d address and the order in which I’d address them.

Cold air intake: I saw a 1.5 mpg improvement on my all-stock ’99 Cherokee by adding a K&N FIPK (fuel-injection performance kit). You’ll also notice a good bump in the off-idle acceleration. You don’t have to run the K&N specifically, but that’s what I went with and it worked for me.

Ignition: The stock components are adequate, but check their condition. Plugs, cap and rotor, and wires should be in good shape. If your wires are the factory ones they may be costing your some power. There are a lot of fancy aftermarket plugs out there like E3, Split Fire, and so on, but I usually just run stock replacements from the local auto parts store. On my GM engines I normally run AC Delco, but I’ve found Chrysler engines do okay with Champions or Autolites. I think I ran Autolites in my ’99. As for the ignition components, I’m a big fan of the Performance Distributors stuff; it’s really good. The company’s Firepower 4.0L kit would allow you to open your plugs to as much as 0.070-inch for a hotter spark and more complete burn of the air/fuel mixture. Accel also has a tune-up kit that includes plugs, wires, cap, and rotor, but I’ve never used it; once you add the hotter coil, it’s almost the same price as the Performance Distributors kit.

After-Cat Exhaust: I used the Gibson Performance system on my ’99 because I didn’t want an obnoxious, droning fart-pipe exhaust. The Gibson one was the only cat-back system I found at the time that offered a quiet muffler that wasn’t just a straight-through design. The system really made a difference in the seat-of-the pants power. The company offers its cat-back with the smaller straight-through muffler, but if you’re looking for a straight-through and don’t mind a little more noise, the Dynomax after-cat exhaust in aluminized steel will be much less expensive.

Tires: A stock passenger-SUV type tire like a Michelin LTX M/S in a 225/75R15 size or Continental’s new Cross Contact LX20 tires on some stock Cherokee aluminum wheels (I like the ’99-’01 15x7 “Grizzly” wheels myself) will offer lower rolling resistance and lighter weight than a regular off-road tire. If you do decide to go to a dedicated off-road tire, make it an all-terrain with a mild tread patter like a BFG AT, Mickey Thompson MTX, or something of that ilk. Again, I wouldn’t go any bigger than 225/75R15 (about a 28x9.50R15) with the stock suspension for max mileage.

Header: If your stock exhaust manifold is cracked (almost all of ’em are), your O2 sensor is probably reading the increased oxygen making its way into the exhaust stream through the crack and throwing more fuel at the engine because it thinks it’s running leaner than it is. I had that situation on my ’99. I installed a Gibson stainless-steel header, but found after about 20K miles it had cracked because my air/fuel ratio was a bit off. (I was running a stroker without a custom computer tune.) Regardless, I swapped out the Gibson for a Banks header and never had another crack. The power (both seat-of-the-pants and dyno) was virtually the same between the two headers. I think the Banks made about 3 lb-ft more on the dyno with identical horsepower. A slightly lower cost alternative would be Edelbrock’s 4.0L header with the company’s TiTec finish. The finish doesn’t peel and burn off like paint.

Once all that’s done you can start refining things down. Run some quality fuel-injection cleaner through your fuel system to remove any gum and varnish from your injector tips. Or, have the injectors professionally cleaned. The spray pattern can get clogged from years of fuel varnish. A finer mist from clean injectors will atomize better and be easier to burn in the cylinders. You can also try changing your fluids over to full synthetic, although I’m not sure you’ll see any real mileage gains. I’ve run Amsoil and Royal Purple synthetics in the past with excellent results. Changing your front and rear axle lube, T-case ATF, and AW4 auto over to compatible full-synthetic can help the internal parts spin more-freely and can reduce parasitic drag. The result may be worth .5mpg, which wouldn’t really help recoup the cost of the lube. Maybe do the synthetic only if you already need to do the fluid change for normal maintenance.

My ’99 with only the K&N and some stock 225/75R15 tires at proper pressure pulled down about 25 mpg if I was able to keep the speed down around 60 mph. It was painfully slow, but bumping the speed up past 65 mph put the poor aerodynamics of the vehicle into play and mileage went down to the 19-20 mpg range. Not great by comparison to most economy cars, but for a boxy five-passenger SUV, I wasn’t about to complain.

1997 XJ Wiring Weakness?
I have a quick question. About your XJ buyer’s guide (“Paycheck XJs,” Jan. ’10), it says to avoid the ’97 models because of the wiring harness.

I just bought a ’97 XJ with a manual tranny for $1,200. I thought it was a good deal since I really wanted one with the AX15, and it was almost impossible to find one cheap.

The XJ needs a new suspension, so it is just a better idea to get a lift kit instead of replacing the stock shocks, leafs, and so on. I have my eyes on the Rubicon Express 3.5-inch Super-Ride system with the full leaf packs.

But since I read that story, I’m not sure if it’s a good idea to invest in this ’97 XJ, or wait to get a ’98 or earlier XJ to modify.

Is the wiring harness in the ’97 XJ a huge deal? Or for the price I got, is it well worth it? What common issues might I face regarding the wiring harness?
Philip Leake
Via email

Hazel and I agree that you should not sell the ’97 XJ because of any weaknesses in its wiring harness. Pete is a wiring guru and has told me that the ’97 XJs and TJs have a somewhat inconsistently weak wiring harness. The harness was changed a few times throughout the ’97 model year. Thus, some may have first year “jitters” depending on the iteration. I would not sweat it if I were you. I spent a looong time a few years back looking for a ’97-’01 XJ with a five-speed manual and ended up owning a ’01 4x4 Sport with an NV3500. Fun Jeep! The post-’96 XJs with the manual trannys are hard to find, and $1,200 ain’t too bad of a price for one. Now if there would have been an identically optioned ’98 or ’99 XJ next to yours at the used car lot, you prolly shoulda bought the newer XJ. My first XJ was a ’97 4x4 SE with a 4.0L and an AW4 four-speed auto. It had a tough life during the time I owned it. I drove the thing hard all across the country both on- and off- road and never had any issues with the wiring (or anything else, really) despite regular beatings.

The Rubicon Express 3.5-inch Super-Ride suspension with the full-leaf pack is a great product, and what I ran on my ’01 NV3550-equipped XJ. More recently, Rubicon had some issues with noisy control arm bushings, but the company is now under new ownership and it’s said it is addressing this issue. If that scares you, run the Rubicon Express springs with shocks of your choice and add a set of JKS control arms. Hazel and I are also in agreement that JKS control arms may be the best short-arm option available today.

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