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July 2012 Your Jeep Tech Questions

Posted in How To on July 1, 2012 Comment (0)
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Jp’s Opinion Angle
I am going to be installing a Wagoneer Dana 44 front axle and a Honda Passport Dana 44 rear axle in my ’91 YJ. My question is, how do you determine the angle of the rear axle? The Rough Country lift that I will be installing already has angle shims attached to the springs, but I will need to weld perches on the axles and would like to know how to set the angles. I am also installing a Rugged Ridge slip yoke eliminator.
Craig Warner
Mason City, IA

Assuming your slip yoke eliminator will require a double cardan (or CV) rear drive-shaft, you basically want the pinion of the rear axle aimed just about 1-degree under the driveshaft angle. That will compensate for pinion climb under acceleration and should place the pinion directly in line with the rear driveshaft. If you’re not using a CV rear shaft, match the pinion angle to the angle of the T-case rear output yoke.

To set the pinion angle, assemble the new axle on the new spring perches and leaf springs (without the shims) mounted to the Jeep with the shackles you plan on using. Longer or shorter shackles will change the pinion angle a little. Center the axle under the Jeep side-to-side and tighten the U-bolts just enough to keep everything in place. To set the pinion angle, allow the full weight of the vehicle to rest on the tires and bounce the suspension a couple times to get it to settle. Then, use a floor jack to move the pinion up or a rubber hammer to move the pinion down. The U-bolts need to be tight enough to support the Jeep but loose enough for you to be able to rotate the axle. Basically you want an imaginary line passing through the axis of the rear pinion (or perpendicular to the axis of the axle u-joint) to be aimed one to two degrees below directly at the rear output of the T-case. Once you have set this angle you can check to see that the axle is still centered and then tack weld the new spring perches to the axle. Then, support the Jeep and disassemble the suspension enough so you can finish welding the perches to the axle. Once driving, as you accelerate your Jeep the pinion will go up a degree or two and should be just about perfectly in line with the rear of the transfer case and thus vibration free.

I Have a Gas Problem
If I remove the catalytic converter from my ’97 Wrangler and install a test pipe, what effect would I have on the engine’s performance? And, would I have any warning lights on the dash as the catalytic converter has an O2 sensor attached?
Drakester
Via jpmagazine.com

If you remove an O2 sensor your Jeeps OBDII system will throw a code, and your engine may suffer from a loss of performance and mileage since the engine’s computer gets info on how to run from the exhaust gasses. Ew! Removal of a catalytic converter from your exhaust system may allow a tiny increase in horsepower at the top of your engine’s rpm range, but it will also probably cause a drop in your max torque at a lower RPMs (which is generally more important than high rpm horsepower to a Jeep being used off-road, or driven on-road the way most people drive on the road). This loss in torque will probably be more noticeable than any gain in high-RPM horsepower). Modern catalytic converters actually flow pretty well and don’t really limit power through the rpm range that much.

I wouldn’t remove it if I were you. If not just for the reasons above, it is also illegal in many areas around the U.S. and can carry stiff fines if you are caught. It also can make selling your vehicle more difficult, as the new owner won’t want to have to pay for the cat to be replaced or worry about any emissions standards they may have to meet.

If it is rattling, then it may need to be replaced, in which case you can either have it replaced at an exhaust shop or do it yourself if you are experienced with exhaust work. You can get a new replacement cat for your Jeep for $100 to $250. These will either be weld-in, clamp-in, or maybe bolt-in.

You’ve Been Framed
In your Aug. ’11 issue, you had an article on building a frame for a CJ-5. Do you have the lengths for an ’86 CJ-7? I’m going to build one after I saw you article. Please send lengths if you have them. I am a reader for years and am very satisfied. Keep up the great magazine!
James D Watjen
Via email

James, unfortunately the way we built the frame for the Ground-Up project won’t work for a later CJ-5, CJ-7, or any of the Wranglers because all of those frames get wider towards the rear of the vehicle and have two (or more) lateral or side bends per framerail. That would require bends in the rectangular tubing which requires a very expensive machine or angled cuts that would then require but-welded joints, which are generally a bad idea on a home built Jeep frame. You can get a new frame for your CJ-7, though. Check out Throttle Down Kustoms (throttledownkustoms.com) or Quadratec (quadratec.com). Another option would be to find and modify either a YJ or TJ frame to fit your CJ-7.

It’s an ’87-’95 Jeep MXJ
I have an ’87 Comanche with a tired 4.0L and blown BA10 tranny. I bought a 4.0L out of a ’95 XJ. I want to also get an AX15 with an NP231.I was wondering, what is the easiest way to wire it? Can you run the engine and transmission on a computer from ’95 XJ, which I would have to find? Would the gauges from my Comanche work?
Dgotj
Via jpmagazine.com forums

Dgotj, that’s an interesting name. Is it German? The short answer is yes you an get the ’95 H.O. motor to run in your MJ as an H.O., but it’s probably not worth the time, money, and effort involved. The long answer is if you had a ’95 donor XJ and a year’s worth of weekends you could probably swap and splice enough of the ’95 Cherokee’s electrical system into your Comanche to get the H.O. to run. It’s possible, but not easy or simple. If you want a long project we suggest you search for info on the website, NAXJA.org. You also can get the Renix fuel-injection system to run the ’95 block if you swap all your Renix stuff over including the head. Lastly, you may be able to get the Renix system to work on the H.O. intake and head with some modification to the intake and throttle body for the throttle position sensor (TPS) and idle air control (IAC).

The AX15 is a much better tranny than the BA10 and should be available rebuilt locally (for less cash than the BA10) as they were used in many Jeeps for many years. Ditto on the NP231. By the way, NP231s are easy to work on and rebuild yourself. Parts are easy to get too! Just make sure you have a good set of snap ring pliers!

Pardon Me, I’ll Have an MT for the Road
I was just wondering what your favorite mud-terrain tire is that is street-practical; like the BFG MT KM2, Toyo MT, TrXus, and so on.
Justin
Via email

If you’re looking for good on-road manners with little road noise, the Toyo MT are your animal. They’re really quiet on-road and work very well off-road. The downside is they tend to wear relatively fast. However, this is true of most MT tires.

We like the BFG MT KM2 off-road, but they’re noisy on-road, so if that’s an issue for you they may not be ideal. Most MT tires are noisy, some more than others. This has less impact on a soft topped Jeep where noise is a constant companion while moving above 30 MPH.

Most Interco tires (even the ones geared towards “good” streetability) are generally uncivilized on the street and wear quickly. That said, Editor Hazel did lots of daily driving a set of 31x11.50-15 Swamper LTBs on his’89 Wrangler, but the compromise is shorter tread life, flat-spotting, and howling on-road ’cause they’re so bitchin’ off-road.

Other ones we’ve used and liked: Firestone Destination MT, Kumho Road
Venture MT, Maxxis Trepador Radial,
Cooper ST Maxx, ProComp Radial Mud
Terrains, and the Dick Cepek Mud Country.

AW4 2WD to 4WD Via NP242
First of all, I just wanna start by saying I love your magazine. I’ve learned so much about Jeeps since I’ve subscribed I think I would be lost without you guys. I subscribe to a couple of forums also, and sometimes it’s tough weeding through the advice and opinions to get some real tried-and-true wisdom. One of my forum friends did a 2WD to 4WD conversion on a Cherokee XJ. This interested me because while it does perform surprisingly well off-road, my XJ is 2WD. I’ve done all my homework, I know which axles I want, I know which transfer case I want and I’ll be going with a mild 3-inch Skyjacker lift and 31-inch tires. I also read your write-up on the MJ 2WD to 4WD build. The question no one can seem to answer for me though is this: I have an AW4 transmission with what would appear to be a removable tailshaft. Is there a way to use this for my conversion or will I absolutely have to change the transmission? I’d like to use a NV242J as the transfer case. Will this affect anything?
Justin
Ocala, FL

Justin, Thanks and you can trust us. Some forums have “Jeep experts” who will lend advice on something that they have no real experience in. Regarding the AW4, I have often wondered this myself. I have never torn into one and for all I know what you are proposing would be an easy swap if you had the parts, but here is the catch. In order to convert a 2WD AW4 to 4WD you’d need a similar if not same year 4WD AW4 for parts, so if you had a 4WD AW4 for parts why not just use it! You’d probably have to pull the 2WD tranny to work on it anyway, so just swapping out the whole shebang would seem easiest to me.

You can easily use a NP242J in the swap just make sure that the stick-out length and splines of the input shaft of your NP242J match the t-case that came with the 4WD AW4.

Comanche Buyin’
I’m thinking of buying a ’91 Comanche that is for sale locally. The truck seems to be in very reasonable shape. I just don’t know much about them. Are there any particular problem areas I need to look for specific to this model? Are there any different axle problems or options from the factory that could be a deal breaker?

Also, I have no plans of leaving this truck stock if I purchase. There are a few aftermarket lift kits for the Comanche specifically, but would products designed for Cherokees work with little or no modification?

I would like to run at least a 31-inch tire, but no bigger than a 33 inches. I would like to know I could install lockers in the front and rear axles without a full-blown axle swap. I live in southern Georgia, so there aren’t really any huge rocks to crawl, but plenty of wet, sloppy trails in the deer woods.
Justin F. Nelms
Georgia

Yea, so a ’91 MJ is going to be a pretty sweet score. The ’91s were the first year of the H.O. 4.0L inline sixes while ’92 MJs were the last year for the MJ all together. The ’91-’92 MJs are generally the most sought after because of this. I have looked at lots of Comanches over the years, and have seen ones that are both in great shape in the South and some that had rusted to bits. I’d say your best bet is to keep a close eye out for any areas of significant rust and or structural damage from an accident and avoid any MJ (or XJ, ZJ, or WJ for that matter) that shows signs of either. As for a lift, I would look to lift your MJ about 3 to 3.5 inches. This amount of lift is perfect for 31-inch tires and can be made to work with 33s, given proper bumpstop lengthening and some fairly significant fender trimming. Now, one complication is that MJs differ from their more common Cherokee siblings in that the rear suspension is different. The rear springs are longer and come from the factory in a spring-under configuration. This means that you will need to look for a Comanche-specific lift kit.

For the lift you will need longer shocks front and rear, front springs, a set of lower front control arms, new rear leaf springs would be nice, or more likely add-a-leaves, new U-bolts and maybe new, longer, rear shackles. I have found that long, thin add-aleaves are usually not too stiff. Combined with longer shackles, they can be a pretty good compromise if full replacement spring packs are not available or cost too much. Lots of people like to do just a spring-over in the back of MJs, and that can be a sweet setup. However, it lifts the rear by a fairly large amount (5 to 6 inches), and though we won’t go into it here, can open up a whole new can of worms regarding the front matching that height. Not to mention potential for axlewrap.

As for lockers, depending on your axles we may or may not recommend some lockers for you. If this ’91 MJ has a rare rear Dana 44, lock it up. If it’s the more common Dana 35, don’t bother. As for the front axle, it’s certainly a Dana 30, which would be great with a Lock-Right or limited-slip differential and 31- to 33-inch tires, but you may break shafts or U-joints if you are hard on it. If the Dana 30 has a center axle disconnect, make sure it’s functioning before you hit the trails, and contemplate swapping it for a ’95-or-newer XJ axle. The newer axle should not have the center axle stuff (which is prone to fail) and should have larger and stronger axle 760X-size U-joints instead of the smaller 260X-size U-joints of the ’91 Dana 30.

Takin’ the Winch or the Strap?
I have a ’00 Jeep Wrangler TJ 2.5L with a 2-inch spacer lift and 31s. I was wondering what you think about me adding an 8000lb winch to my Jeep. I live in an area that has a wide variety of terrain. The winch would be used for moving downed trees and for when I get stuck. Or do you think a tow strap would work better?
Tom Renyolds
Wentachee, WA

Honestly, it depends on how much you drive your TJ on-road and if you wheel alone or with others. If you always wheel with others who could give you a yank with a strap you will save yourself lots of coin and go with the strap. If you wheel by yourself, a strap will be useless if you get stuck. In this situation a good working winch can be a life saver. Straps can be great for moving downed trees out of the way, but a winch can do that too—and more safely! If you daily drive your TJ for long distances on-road, the added weight of a permanently mounted winch may cost you a little at the pump. A strap is light and strong and essential even in Jeeps that sport a winch. When looking for a strap, avoid the ones with hooks on the ends. They can be killers if the strap breaks, the hook breaks, or the mounting point yields. We prefer 3-inch-wide flat straps with loops at either end for use in our Jeeps. You can use a large D-ring to attach it to your Jeep, just loop the end around a hook or wrap it around a bumper and back through itself. As for a winch, look for one built by a company that will stand behind its product. Nothing is worse than a cheap non-working winch in the middle of nowhere.

Powered By Liberty
I have a ’90 YJ with a 2.5L four-cylinder. I have acquired a 3.7L Jeep Liberty engine with transmission and transfer case. I was thinking of switching the four-cylinder for the V-6. Now the nuts and bolts of the swap I think I can figure out, but I have no idea how to do the electronics. Do I need the sensors to make sure everything is working and to be able to see what it is if something goes wrong? I can identify the sensors, but I do need some help. Thanks!
Josh
Shelby, IA

Wow Josh that’s a new one—for me, anyway. I hate people who say you can’t do something. I’m not gonna say you can’t do this, but I don’t think I would. It’s probably not going to be a quick or easy swap and it’s gonna be a nightmare without the engine computer, transmission computer, and full wiring harness from the Liberty. I am not sure I would recommend it, given the minor increase in power and torque for the headache you are creating for yourself. Basically you are gonna have to make the Libby engine and tranny think that they are still in the KJ. You will need all the sensors from the Liberty, and you may want the gauge cluster. There is some chance that the guys at Hotwire Auto (hotwireauto.com) would be willing to take a stock Liberty wiring harness that you supply them and pare it down to make it work with the KJ computers in your YJ as a stand-alone unit. However, the time and monetary cost would likely be better spent on a V-8 swap.

15x8 vs. 15x10
I have an ’05 Wrangler TJ with the inline-six and six-speed manual transmission. Currently I have a new set of 30x9.50R15 w BFGs I acquired from the dealer and I just put a Rusty’s Off Road 2-inch coil lift. I also have a Daystar 1.25-inch body lift. I want to run 33x12.50R15s but since my 30x9.50R15s are still good I was wondering if I can run both 30x9.50R15s and 33x12.50R15 tires on the same wheel size of 15x8? I’m wondering if airing down will cause beads to pop on the 12.50-inch-wide ire on an 8-inch-wide wheel. I hate my stock gray steel wheels and want to run some black steel ones. Discount Tire keeps aying I need to use 15x10 wheels, but I think they just want a bigger sales price.
barts.83chevy
Via jpmagazine.com

Bart, 15x8s are fine with 12.50-inchwide tires.

3KTJ 4 Real!
It’s almost as if you guys wrote “3-Day TJ for $3K” (Apr. ’12) for me! I bought my ’06 Wrangler X shortly after my combat tour and am now a working man with an earmarked tax refund. In the article there are lockers, winches, gas tank skids, and even flashlight mounts. What about the transmission skid? I find that the hunks of ribbed steel that hangs obscenely beneath the stock TJ is the biggest drawback in snow, sand, mud, and rock. I was hoping to see what you suggest to replace this hunk of junk?

The returning Jeepers might also like to have recovery points, front and back, to hook those straps and winches to. This maybe extra important if they start pushing the limits of their newly equippedJeeps. I know my stock Wrangler didn’t even come with the front hook shown on the subject TJ. Most of my local Jeep and 4x4 clubs require them anyway, so I thought they might have been added to the list. In short, I appreciate the article. Although, I feel a new transmission skid-and recovery points are far more cost-effective than some of the things on the lists, this was a well-written article from a great magazine.
Aaron Fleck
Via email

Aaron, Thanks for the letter and thanks for your service! I totally agree with what you say about towhooks. Honestly towhooks are something every Jeep should have rolled off the factory assembly line with. Hell, even Hondas have tow points for when they end up in the ditch, so why don’t Jeeps have hooks to pull all those Hondas out of the ditch? If you want hooks here are some part numbers from Quadratec. Front PN12007.99 13230, Mopar front: PN12107.99. The rear is a little bit tougher on a TJ since there are several options including a stock-type towhook. I prefer using something that can accept a 3/4-inch D-ring shackle that mounts on the -back of the rear crossmember of a TJ or via a receiver hitch. This is because a hook will either be below the rear crossmember or on the side of the frame and will be difficult to get to, especially in mud.

As for the skidplate I do plan on upgrading from my factory piece for a future tech article in Jp . You’ll have to wait and see what I do for this! My plan for the Jeep is to continue to build it up with budget ideas that will improve its functionality without costing an arm and a leg and without building it to the point that it needs to be trailered everywhere. I wheel the pee pee out of the thing, and it’s a ball!

Dimple Die Underhood Cooling
In the story “Jeep Tips & Tricks For the Trail” (Mar. ’12), you mention creating cooling holes with a die. Do you know where the die came from that made the holes in that hood? They look very good. Thanks for your time.

If you have an answer for this could you please email me the answer? I’m currently deployed in Kuwait and may miss the answer if it’s just published in Jp magazine.
Micah
Kuwait

We found a few sets and individual dimple dies from Summit Racing (summitracing.com). These dimple dies are used in conjunction with a hole saw. Basically, you decide where you want your hole, use a hole saw to cut the hole, insert the dimple die’s two halves (your hole size must match the die, i.e., 11/2 inches in diameter) and apply pressure with a press. The dimples add a racy look, but also add rigidity to flat sheetmetal, or, as in this case, allow a path for air to enter or escape an otherwise enclosed area. Thanks for your service!

J-20 Resurrection, Carolina Style
I’ve got a ’72 Jeep J20 and I was wondering if you guys could tell me a good place to get aftermarket parts for the truck. I’m looking to redo the truck.
Dwayne Capps
Gastonia, NC

Dwayne, cool truck, I just bought a ’78 J-10. (“Piggy’s Revival”, page 30 in this issue). Hope it’s not too rusty! Luckily for you and for me there are a few places to get parts and info on these old rigs. First, check out BJ’s Off Road (bjsoffroad.com) and the website IFSJA.org for more info than you may ever need on these and other full-size Jeeps! For info, you can always use the Googles on something these kids are calling the interwebs. Also check out Crown Automotive ( crownautomotive.net ).

Write Us!
Got a tech question you re just itching to get answered? Send it on in to Jp magazine, Your Jeep, 831 S. Douglas
St., El Segundo, CA 90245
or e mail it to verne.simons@jpmagazine.com . www.jpmagazine.com

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