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November 2008 Your Jeep - Tech Questions

Posted in How To on November 1, 2008
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Mileage Master
I drive 100 miles a day to and from work. I'm trying to find that happy medium between traction and mileage. My jeep is a "Willys Edition" X model with the 3.07 axle gears. With the modifications I've done, I get about 23 mpg.

I'm looking for some tires that will last a while and give good traction, but that won't hurt my mileage. Any ideas would be helpful.Jim KayneVia e-mail

That's really good mileage. Better than I ever got with my four-cyl. YJ on P225/75R15 tires. For your criteria of good mileage, long wear, and good traction, you're going to want to stick with the stock tire size. With the 3.07 gears, bumping tire size up even just a little will cause your mileage figures to plummet about 10-15 percent. A BFG AT should get you what you're looking for. The sizes are available for your stock Jeep and with proper rotation and inflation should last around 40K miles and help you retain your high mpg numbers. The traction off-road is very good, especially when the tire pressure is dropped to around 8-12 psi.

Seeking An Extra Shift
Three easy questions: I have an '03 Rubicon.1.Is the manual six-speed a better transmission?2.Is it a direct replacement for the manual five-speed my Rubicon came with?3.And what are the gear ratios for the five- vs. the six-speed?Paul BiriVia e-mail

1. The six-speed is perhaps a more drivable and civilized transmission, but probably not as durable as the NV3550 your Rubicon came with. The six-speed is a Jeep transmission. The NV3550 is a 1/2-ton truck transmission.

2. It isn't a direct replacement. While there is a provision for a crank sensor, it is in the wrong place and your crank sensor won't bolt in; further, the bellhousing and tranny case are one integral unit. It does share the same T-case spline count, so the NV241OR will bolt to the back.

3. NV3550: 4.01, 2.33, 1.39, 1.00, 0.78, 3.57 (Reverse); NSG370: 4.46, 2.61, 1.72, 1.25, 1.00, 0.84, 4.06 (Reverse).

As you can see, you've got a more durable tranny with a deeper overdrive. I'd stick with what you have. Check out "Six-Shooter" in the June '08 issue for more info on swapping the NSG370 six-speed transmission.

Factory No Fool
I have an '04 Jeep Wrangler Sport (manual transmission) with a 4-inch suspension lift and 33-inch tires. I plan on towing the Jeep behind my cargo van 1,400 miles using a towbar attached to a heavy-duty aftermarket bumper on the front of the Jeep.

The '04 owner's manual (page 205 through 207) says to put the transfer case in Neutral and leave the steering wheel unlocked and the manual transmission IN GEAR. It says putting the transfer case in Neutral disengages both front and rear driveshafts, leaving the transmission free no matter what gear it is in.

The question I have is this: Wouldn't it be better or safer to leave the manual transmission in Neutral also? I don't see the benefit of leaving the stick engaged. I've had several queries out to Daimler Chrysler, and all they did was continue to refer me to those pages in the owner's manual. They refused to add anything or clarify anything. The dealerships don't even know. If something slipped, such as the transfer case, then what? Do you have any particular advice on how to do this as safely as possible? I'm looking for any way to prevent problems since 1,400 miles is a long haul and I don't want to wreck my rig.G. Eberly Via e-mail

Leave the tranny in gear and the T-case in Neutral as the manual says! The reason you do this is to keep the transfer case input from spinning. This is common practice with nearly all Jeeps. It's a little complicated to explain, but essentially you don't want any residual spinning to find its way to the tranny. The parts inside the tranny may not be lubricated properly without the input spinning (engine running). Basically only half of the tranny would be spinning, possibly starved for lubrication.

Trust the owner's manual on this one. It should not accidentally pop into gear while being towed. Make sure you shift it properly into Neutral; I have the same manual and it explains what to do very well. Just make sure you keep stacked luggage and other stuff off of and away from the shifter. -John Cappa

Facelift
I just started reading your magazine and am a big fan. I just bought an '88 Wagoneer (not a Grand Wagoneer) as a side project to work on. I'm stripping the paint, repainting it, lifting it, and putting bigger tires on. The only problem is, the grille on the Wagoneers is pretty ugly with the lines running horizontal and not vertical like a normal Jeep. I was wondering if there was some kind of a kit or some way to switch out the grille with a normal Cherokee grille without having to move the lights around (the Wagoneer has the turn signals mounted into the bottom corners of the grille) or hack things into place. If you have any ideas they would be greatly appreciated.Jeanette AnrayVia e-mail

I've never tried it myself, but I know the fenders are the same from '84-'96. This leads me to believe you should be able to snag a front clip from a junkyard XJ and bolt it in place of your Family Truckster front end. You'll probably need to wire and splice the headlight connectors from the donor vehicle in since yours has four: two for the high beams and two for the low beams. I'd also see if the radiator core support can be unbolted. I don't have my Cherokee here right now or I'd check for you. If so, just unbolt the core support of the donor as well to ensure you won't need to cut and hack for the dual headlights.

Daily Driver Dilemma
My wife wants a lift on her '98 XJ to clear 31s. I want a dependable lift (no add-a-leafs) but like everyone I don't want to break the bank. I was considering a Rusty's or Rubicon Express lift. The XJ will see very limited (if any) off-road time. Do you prefer any one lift to another? Can I get away with a 3-inch lift with no slip-yoke eliminator? Would I need to replace the control arms if the kit doesn't come with any? I wanted to keep it around $1,000-$1,200, including tires. Any input would be greatly appreciated.Matt StellMarietta,GA

Hey, Marietta. I used to live in Woodstock. Is the Big Chicken still there or did they tear it down?

I recently dusted off Jp's '99 XJ and am going to replace the Full-Traction 6-inch long arm with a short arm suspension with less lift for use with 31s, so I've been going through the same thing you are.

I decided on the Rubicon Express 3.5-inch system (PN 6025) because I need new control arms to replace the long arms the Jeep currently runs. I'll still need to get uppers, but I should be able to find some factory uppers free at my local off-road shop. I've used RE products in the past and really like the company's leaf spring design, so that's why I've decided on the Rubicon Express suspension for Jp's Jeep. However, at almost $600 without shocks, I don't think this kit meets your criteria for keeping the whole budget under $1,000.

There's nothing wrong with the Rusty's kit. The company makes a really nice product. I'd consider RK-300SP-XJ, which doesn't include control arms or driveline corrections, but at under $500 with shocks, springs, and brake lines, leaves a lot of room for buying wheels and tires. You shouldn't need new control arms at this time, although you'll probably want to eventually upgrade for the added adjustability and strength of aftermarket arms.

With either of these kits, I really would suggest eventually adding a slip-yoke eliminator. You can drop the transmission to alleviate vibration temporarily, but for the best longevity, I'd plan on eventually adding a slip-yoke eliminator and CV-type rear driveshaft.

Overpriced Auto
The article "200,000-Mile Club" (Mar. '08) is great. I am looking for a project/fixer-upper and I am using the article as a guide. I am able to get my hands on a '98 TJ 2.5L auto for $6,500. I know, I know what the article says ... so here is my question: How much work and how much trouble would it be to swap in a manual? And do you have any advice on transmission choices? I am on a military budget (small) and I am not a professional mechanic, but I am a member of a Jeep Club and we have project parties. Again, any advice would help and if you say run away from this Jeep, I'll listen-after all, I am used to following orders!Rob ThomasSuffolk, VA

For starters, that's about $3K too high for a '98 four-cylinder TJ unless it's only got 50-60K miles on it. Second, forget the auto behind the four-cylinder. It's a miserable combination. You can swap to a manual using an AX-5 from another four-cylinder TJ, but they're not durable and chances are the tranny you install is gonna blow up at some point. The AX-5 is usually only good for 100-150K miles before it needs a major rebuild.

Advance Adapters sells a conversion kit to put a stronger AX-15 from a 4.0L Jeep behind the 2.5L. If you do buy the Jeep, that's what I'd recommend. Regardless of which transmission you go with, either will require a new engine computer from a '98 manual transmission 2.5L TJ. The factory auto tranny computer can't be reflashed and it'll constantly be throwing a check engine light because it won't be receiving a signal from the lockup torque converter. You may be lucky enough to find a used one online, but most likely you'll be buying a $450 replacement from a company like ECU Direct or similar.

In short, keep looking. There are better deals out there. You should be able to find a '97-'99 2.5L TJ with a five-speed manual in the low/mid $4,000 range with 100-150K on the odometer. At that mileage you'll still have at least 100K before the engine will need anything major. Or you could focus on finding a '91-'95 4.0L YJ. They routinely go for $3,000-$4,500 in decent condition.

Long, Long, Long Distance Shopping
I am currently trying to slowly upgrade my '00 XJ. I am looking for a complete exhaust system from header to tailpipe. I mean I want everything-downtube, muffler, header, catalytic converter, even the damn clamps and the exhaust hanger. Here is the conundrum. I have found that if a company, such as Banks, makes a header for the '00 4.0L, it makes nothing else. No downtube, no after-cat, nothing. What gives? Is this to keep the EPA off their backs? Back to my original need, can you send me to, or recommend me a one-stop source for a complete system? I would like to put it all on myself so I would like to do this with parts that are known to fit right. I would also like it to be a single manufacturer, but that is looking to be impossible at this point.Robert C. GreenFOB Kalsu, Iraq

It's not for liability-it's just not cost-effective for companies to R&D and manufacture a kit for the Cherokee (and Jeeps in general) because of fitment issues. They're such a highly modified vehicle that the manufacturers don't want to deal with customer complaints. You gotta figure a lot of people buy Jeeps with aftermarket suspension components, and so on, and don't even realize they've bought a modified vehicle. Then they get bent when the parts don't fit. There's also the fact that there were a fair number of chassis and exhaust changes on these vehicles through the years. Also, companies aren't able to charge the same premium price for a Jeep system as they could for, say, a Hummer or Corvette. I can't see too many Jeep owners shelling out $3,000-$5,000 for an exhaust, but Corvette guys do it all day long.

Your best bet for a complete exhaust system is going to be your local auto parts store, your Jeep dealership, and maybe a few aftermarket companies.

I checked Napa's web site for you. Here's what I was able to find: Cat convertor: PN EXH 16117 - $210 Dynomax after-cat system: PN EXH 17340 - $170 Gasket (converter to downpipe) - PN FPG 60292 Gasket (2) (header to downpipe) - PN EXH 31362 - $16.69 ea. Exhaust Hanger - PN EXH 36152 - $9.99 Exhaust Clamp - PN BK7335336 - $1.69 Exhaust Hanger (2) - PN EXH 36377 - $12.79 ea. Exhaust Isolator (2) - PN EXH 35460 - $4.39 ea. Pipe - header to cat (for header w/ dual outlet - replaces pre cats) - PN EXH 54450 - $93.49 Pre-cat assembly (if can't use straight pipe above) - PN EXH 52304 - $209 Intermediate pipe (between pre-cats and cat convertor - PN EXH53440 - $109

You'll probably want to double check those part numbers in person once you get back to the States since there were a bunch of other options with the hangers and so on, but as you can see you can pretty much piece together the complete system from your local Napa. Another option if you have a good exhaust shop you trust would be to drop the Jeep off and have one built. This would be the way I'd do it. That way you can have a complete 2.5-inch system built with an OBDII cat and it'll flow a lot better than any store-bought system. Just make sure to ask the shop to see some examples of their work before you trust their skills on your Jeep.

Got a tech question you're just itching to get answered? Send it on in to Jp Magazine, Your Jeep, 6420 Wilshire Blvd., Los Angeles, CA 90048, or e-mail christian.hazel@jpmagazine.com.

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