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June 2005 4x4 Tech Questions - Tech Questions

Posted in How To: Tech Qa on June 1, 2005 Comment (0)
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June 2005 4x4 Tech Questions - Tech Questions

Address your correspondence to:
Techline
Four Wheeler
6420 Wilshire Blvd.
Los Angeles, CA 90048-5515.

All letters become the property of Four Wheeler, and we reserve the right to edit them for length, accuracy, and clarity. The editorial department also can be reached through the Web site at www.fourwheeler.com. Due to the volume of mail, electronic and otherwise, we cannot respond to every reader, but we do read everything.

Question: Over the years you have given me succinct advice on each new XJ that I have owned, including an '87, a '93 and the last of the line, my '01 Cherokee Sport.

For perspective, I sometimes pull a 2,000-pound trailer, don't get way off-road too much these days, but do some desert exploring here in Arizona. I do travel to the Colorado San Juans and took my '87 on an early Hole-In-The-Rock Jamboree (and survived!).

As Jeep vehicles become only "trail rated," the Cherokees have become history, and Grand Cherokees are next, bigger and heavier-again! Now we see an IFS and a switch to electro-diffs on the new bloated version.

One simple question now: Is owning an '01 Command-Trac auto Cherokee better than running out to buy one of the last '04 Grand Cherokees with the Vari-Lock 4x4? Please give me some good advice on which choice is the "keeper" for the next 10 years or so.
Steve Owen
Chandler, AZ

Editor: The Vari-Lock on the Grand Cherokee is a really great system for what it was designed for-street use in bad weather, like snow and rain, and some not-so-serious 'wheeling. OK, with those words, I am going to get a whole bunch of letters telling me just how great their Grands are. And I will agree. If I could afford one, I would be driving an '04 instead of my '96. But I also get letters telling me that there is just way too much wheelspin before the system locks up.

The benefits of the new Grand are a great new engine with lots of performance that would do a great job of pulling your trailer, along with ride and comfort levels way beyond anything you will ever experience in your Cherokee Sport. They also make pretty decent off-road vehicles.

Question: I have a '78 Scout II 4x4 which I would like to change into a 2x4 desert rig. My problem is that I can't decide whether to use a solid I-beam front end or a Ford twin I-beam front end. The twin would be more work to install, but it would make for a better ride on rough trails. Which setup do you think would be worth the time? Or do you have any other better ideas?
Brandt Dietz
via fourwheeler.com

Editor: First off, why would you want to use a Scout as a go-fast rig in the desert? No, I don't have anything against Scouts and even built one as a project vehicle for this magazine and have owned at least four IHs. It's just that they are very nose-heavy, due to the "truck" V-8 they use and its forward mounting location. The IH engine is a torquer, not a high revver, the last being something that is handy in high-speed desert running.

I assume that when you say a solid-beam front end, you intend to use leaf springs. Well, that would be the easiest swap, as there were two-wheel-drive IHs made with a solid front straight axle that used the same leaf-spring suspension as the four-wheel-drive versions. While you would lighten up the front end somewhat, as well as the over all weight without a driving axle and a transfer case, I doubt that you would see that much difference in the handling. The twin I-beam conversion (I am assuming would come from a Ford truck), would be quite a difficult conversion, partly due to the engine's forward location. Nothing is impossible, but it would be a major undertaking. Do keep in mind that the Ford's track is wider than that of the Scout, so modifications to the arms would have to be made, or wheels with quite a bit of backspacing could be used to keep the track the same as the rear.

If you really want to go fast, the answer is to copy some of the Unlimited Class race trucks and go with a long-arm true independent suspension along with coilover shock units. Again this would take some major design and modifications along with a large amount of money.

Any better ideas? Yep, keep the driving front axle, modify the leaf springs so that the shackles are now at the rear instead of at the front of the spring pack, and enjoy-especially so when your two-wheel-drive buddies are stuck and you just pull the transfer-case lever back and motor on by them.

Question: I'm 14 and have been off-roading since I was born. I was looking at "The 10 Monster Rigs for the TTC" (Oct. '04) and I saw the '94 Chevy Suburban with the Dodge Cummins engine under the hood. It's said to have 3,400 lb-ft of torque. How in the world would you get that much power? Not even my dad's semi has that much power, and we pull 48-foot trailers that weigh 32,000 pounds, and when loaded, their weight is 85,000 pounds. So my question is, if a Dodge engine can have more torque than a semi, what would you have to do to make a semi have that much torque-as in 3,400 lb-ft of torque-or can you just not do that to a semi?
Emery Andrus
via e-mail

Editor: Nice catch. Somehow, that either was a misprint or wishful thinking. However, I was at a recent dyno test where I saw several modified Dodge/Cummins engines make in excess of 800 lb-ft, and one made an almost unbelievable 921 lb-ft and 442 hp!

This particular engine, I believe, used two turbochargers and a nitrous system to make this kind of power. How long the engine will last is anyone's guess. In my opinion, there are only so many horsepower-hours in an engine. Keep in mind your dad's truck engine most likely will have to pull loads like you described for about one million miles before it's time for a rebuild.

Question: I see a lot of trucks with the left-rear shock mounted behind the axle, and the right-rear shock in front of the axle. What's the advantage of this apparently asymmetric arrangement?
Brian Dunning
Laguna Niguel, CA

Editor: I believe that it was Chevy that first made this a popular item. The axle by design wants to pull the pinion snout upward during acceleration and downward during braking. The housing will actually move enough to cause each spring to flex in opposite directions on either side of the housing. The spring, as it bends, builds up a tremendous amount of tension and then releases suddenly. This is often referred to as "spring wrap up." This in turn causes the axle to actually "hop" up and down resulting in uneven traction and can even lead to breaking parts such as spider gears, axleshafts, and teeth on the ring-and-pinion gears.

By exerting force on opposite sides of the axlehousing, one shock works in compression while the other works in extension. While it may not completely eliminate spring wrap up, it goes a long way to prevent it in most situations.

Question: I'm planning a buildup of a '74-'91 K5 (don't have the truck yet). I plan on using a 4-inch shackle flip and 2.5-inch springs in the rear and 6-inch springs in the front. I already have a 14-bolt rear with 4.56 gears and a Detroit Locker, and a Dana 60 front with the same gears and a Dana Tractech. They're military axles that I got for a good price with low miles. I plan on running either 39.5x18 Boggers or 39.5x15 TSLs with plenty of fender trimming.

First of all, are there any glaring flaws with this plan that I'm missing, like not being able to fit the tires? Also, will there be a significant difference between the Boggers and the TSLs because of the width in terms of performance and whether they will fit or not? At 6 to 6.5 inches of lift, will driveline modifications be necessary? I'm a high school student on a tight budget. Should I upgrade to aftermarket axleshafts and U-joints before I even consider wheeling 39.5-inch tires?

And last, are the gears numerically high enough for now? I plan on swapping them out at a later date but like I said, I'm on a tight budget. It has to run about 40 miles on asphalt to wheeling spots and I'm going to have to keep the stock engine which will probably be a TBI 350 if I can manage it. I know that you're probably going to tell me to go with a smaller lift and smaller tires, but I'll soon be a college student on an even tighter budget, so I'd like a rig that I can upgrade as I wheel and not have to buy major components over again like the springs, tires before they're worn, and so on.
Mike Dannenberg
via fourwheeler.com

Editor: Sounds to me like you have a great plan. Unlike a lot of people, you have done some thinking ahead of time. That's a lot of tire, but it should fit with the fender trimming. I sure in heck wouldn't go any larger. I would recommend that you go with the TSLs over the Boggers. While the Boggers work great for what they are designed for, they are not one of Interco's better highway driving tires. They are noisy, wear uneven, and don't handle all that well.

If you plan to take the truck to college with you, I think that the gearing will be just about perfect as it will keep the overall engine speed down to a reasonable level for the best fuel mileage. Speaking of that, don't expect any more than about 10 mpg.

As for going with aftermarket axles and U-joints, probably not a bad idea, but they are pretty darn expensive. The stock pieces are certainly capable of handling most four-wheeling if you drive with your mind and not with your right foot. For instance, axle U-joints lose strength the tighter the angle they work at (actually this is true with any U-joint), so just don't jump on the throttle hard when the wheels are turned to full lock.

As to changing the driveshafts, hopefully you got the matching driveshafts at the same time you got the axles. For sure the rear shaft will have to be shortened due to the shorter wheelbase. Most likely the front shaft will have to be lengthened some. To find the proper driveshaft length, I like to just use the one main spring leaf to hold the axle in place. Let the axle totally compress against the bumpstop and then measure from the center of the pinion yoke to the center of the transfer-case yoke. Then jack up the truck by the bumper and let the suspension totally drop so that the wheels are off the ground. Put some jackstands under the frame and again crawl under the truck and measure between the two yokes. Now you know what the extended and collapsed driveshaft lengths are supposed to be. Yes, it's a lot of work but you know for sure the correct length. This also gives you a chance to see if you have enough clearance for the tires as well as figuring proper shock and brake line lengths.

Question: Going through my magazine collection recently, I noticed the coverage of the 2002 Top Truck Challenge. The portion that again caught my attention was that of the '78 International Scout owned by Abelardo "Abba" Ramirez, nicknamed Terra Cotta.

The interest is due to my own '77 Binder and its rust/clearance issues. I have been looking for cut-out extended flares for nearly 7 years. When I first read the article I realized that they were exactly what I'd been searching for.

The dilemma is that the article does not indicate for which vehicle they were originally made. After considerable research among flare manufacturers, the nearest I can figure is that they are off a '70-something fullsize Chevy pickup.

I've made several attempts to track down the owner via the white pages and have been unsuccessful. If you could help I would be very grateful, either by telling me exactly which flare they are, or better yet, putting me in contact with the owner. Either of these could save me from purchasing the wrong parts. Scouts, as I am sure you are well aware, are not very easy to find parts for, especially for modification.
Shannon H. Hicks
via fourwheeler.com

Editor: Sorry can't help you with a phone number or address and it's not our policy to pass on that information. However, if I remember right, those looked like the Scout flares that are available from Bushwacker (www.bushwacker.com). Now a long, long time ago I used some Bushwacker early Chevy Blazer cut-out type flares on an IH pickup. They actually fit pretty darn good in that they were never designed for that truck. Would they fit on your Scout? I have no idea.

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