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June 2006 4x4 Tech Questions - Nuts & Bolts

Posted in How To on June 1, 2006
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Confused? E-mail your questions about trucks, 4x4's, and off-roading tech using "Nuts, I'm confused" as the subject and include a picture (if it's applicable). Digital photos must measure no less than 1600 x 1200 pixels (or two megapixels) and be saved as a TIFF, an EPS, or a maximum-quality JPEG file. Also, I'll be checking the forums on our Web site (, and if I see a question that I think more of you might want to have answered, I'll print that as well. Otherwise drop it old-school style with the envelope addressed to the address below. Letters published in this magazine reflect the opinions of the writers, and we reserve the right to edit letters for clarity, brevity, or other purposes.

Write to:
Nuts & Bolts,
4-Wheel & Off-Road,
6420 Wilshire Blvd.,
Los Angeles, CA 90048-5515,
fax 323.782.2704

E-mail to:

Question: I am building an '87 S-15 Jimmy. It has a zz383 crate motor, TCI 700R4, 5 inches of lift, and 38.5x11x15 Boggers. This truck will see very little if any road time. Can I build the IFS front end and rear axle to hold up to the mud use it is going to face? There won't be much rockclimbing done, but there will be some trail use. The cost of a solid-axle conversion seems high. If I need to go that route, can you suggest a solid-axle swap kit for me? I would also like to put selectable lockers in this.
Seth Engelhardt, via

Answer: I get an S-10/S-15 question almost daily, and you are this month's lucky choice. I like the idea of keeping your truck IFS for mud use, and since you want to try something different than the old standby solid-axle swap, I chose you as this month's Tech Letter of the Month and will be sending you one of the new ARB recovery bags. (Thanks, ARB. And sorry about the misprinted phone number in the Apr. '06 issue. The correct number is 425.264.1391, When in the mud you want the drivetrain up high so it doesn't catch in the mud and slow you down, and IFS can help with that. Unfortunately, stock S-15 IFS is not strong enough for the size of tires and engine you are throwing at it. Heck, I doubt even stock 1-ton IFS parts will hold up as I keep breaking them in my Red Sled project (see elsewhere in this issue). Plus, most aftermarket suspension kits simply lower the IFS axle and mounting points and do little for ground clearance.

I would build a high-zoot IFS setup by combining a custom-built axle centersection from Currie Enterprises (714.528.6957, or Dynatrac (714.596.4461,, then source some heavy-duty, high-angle halfshafts from Rockford Constant Velocity (, or those being offered by Rough Country ( Then fabricate a custom set of A-arms that would support some sort of portal axle knuckles such as those found on a Hummer H1. This would allow the axlehousing to be mounted to the frame up high and out of the way of the mud while letting the tires droop low into the slop to keep you moving without binding the CVs. Some issues with this plan are that the Hummer portal boxes have been known to break under heavy H1s and may not be the strongest design for the big power you'll be using, but your weight is much less than an H1. To run this style of portal box you would need to flip the axlehousing upside-down to reverse the input into the portal box, and as a result proper oiling must be investigated. Consider the gearing, as the portal box multiplies your ring-and-pinion by 1.92 and that needs to somehow be matched in the rear (maybe with an IRS portal setup). All this results in a very expensive suspension, such that cutting out the stock IFS, inserting some leaf springs, a solid axle, and sorting out the steering, brakes, and driveshaft starts looking pretty easy. Innovation, though at times expensive, is way cooler than following the herd. Nonetheless, I say build it, and show us all how to do it.

Question: I have a '98 Jeep Wrangler with a 2.5L four-cylinder. To get more power out of the four-popper I made the following upgrades: headers from Pacesetter, a Magnaflow muffler, a 62mm-bore throttle body with a 62mm TB spacer, and cold air intake. I even enlarged the opening on the intake manifold to match the 62mm on the throttle body.

After all this, the improvement was not significant. My mileage was the same (OK, maybe better) and the power output was...well, kind of better.

I initially made all the upgrades to get better mileage ( I was getting 16.5 mpg), but now that I have a lift, wheels, and 33-inch tires to install, I'm afraid I'll lose what little power I've gained. I'm willing to give up mileage for power, but what other upgrades can I make on the Jeep to get more power?

Keep up the good work.
C. Gabe

Answer: One of the best ways to get more power from a four-cylinder is to reduce the workload demanded of it. You have done all the recommended engine upgrades, yet we're sure the seat-of-the-pants feel is still not the most impressive, so why not look downstream and consider some gearing changes? We did a quick Jeep TJ buildup a few years back ("3-Day TJ Buildup," June '04). One of the upgrades was 4.88 ring-and-pinions with 33-inch tires. Although the four-banger was far from a fire-breathing torque monster, it would easily turn the tires and creep down the trails.

Another great example is my infamous Toyota Clampy. That truck has over 200,000 miles on the ticker, but the tired old four-cylinder still turns the 39-inch BFG Crawlers just fine since it has 7.17 cogs in the differentials and dual reduction transfer cases underneath. It won't really smoke the tires, but it will happily creep along rocky trails, has enough bump to boost itself over steep ledges, and can still run at moderate highway speeds.

The science of gearing is pretty simple. As your gearing goes lower (numerically higher) you are effectively multiplying the number of engine rotations into one rotation of the tire. Each engine rotation is like one little dose of power. In stock form your Jeep most likely has 4.10 gears, thus when in Fourth gear high range (1:1 gearing) for each rotation of the tire you were getting the power of 4.1 engine rotations. If you lower your gears to 4.88 you are getting 0.78 more of an engine's power-just over three-quarters-per one tire rotation added to each tire. In essence you are reducing the amount of work required by the engine, which will result in a more powerful-feeling truck. Remember that gearing too low will make the engine rev like crazy at highway speeds, and if you are looking for tire-smoking power then there's no replacement for displacement. But if you just want the Jeep to keep up with traffic yet still clear your local trails, lower gears may give you back the pep you will lose by going to larger tires.

Question: I have a stock '86 K10 Chevy. I have an opportunity to purchase an '86 military K5 Blazer. I was wondering if the leaf springs would work on my truck. The Blazer sits up higher than my truck. I am trying to get the truck up in the air without having to purchase a lift kit. Also, are there any Web sites that would have specs on military vehicles? The Blazer is also a 1/2-ton. I want to see if the gears are a lower gear ratio than my stock 3.08. Both vehicles have 10-bolt GM axles.

Answer: Yes, the leaf springs will fit on your truck, but if they are stock they shouldn't have much more lift-if any-than what's in your truck now. It is possible, due to the weight of the diesel, that the front springs are a bit stronger, but we doubt by much. However, there are a few things you should check out before you pull the springs off the Blazer and start the swap. First, does the Blazer have any parts missing such as the engine, doors, interior, tranny, transfer case, or top? If so, the lack of that weight may allow the springs to arch up and appear to be lifted.

Second, does your truck have any extra weight such as a big bumper and winch, a camper, an extra fuel tank, or fat cousins riding in the back causing the springs to sag?

Third, how much mileage is on the Blazer? Hopefully it's low and your stock springs are just worn out. If so you will probably still get years of use out of the Blazer springs, but they still are not really lift springs.

Fourth, does the Blazer have extremely tall or small tires compared to your truck? In either case the Blazer may appear to sit taller when in fact its springs are no better than what you have.

Finally, take a tape measure and measure the distance from the top of the axletube to the bottom of the frame, and see how it compares to what you have. Also measure the thickness of the leaf spring packs. You may have found some special-order military variant that either needed extra weight-carrying capability such as for hauling a bunch of radio equipment or your cousins when they served.

In any case, if the springs truly do hold the frame up higher off the axles than those in your truck do, you should be in luck to get some extra clearance. As for the gears, they should be 3.08s in that Blazer, so instead try to track down the 1-ton axles with 4.56 and a rear Detroit Locker from the military pickups.

Question: How can I put my '70 Dodge Charger's 440 into my '88 GMC Suburban to replace the blown 5.7L? Can I use the GMC tranny/transfer case? Is there a good fuel-injection kit that would replace my carb?

Answer: I think I can help solve your problem. Your head itches not because you have dry flakes but because you're scratching it too much trying to figure out this swap.

First things first. Yes, you can put a 440 in your Suburban, but just because you have the engine doesn't mean it's the best, cheapest, or right thing to do. You would need an adapter between your 440 and the GM tranny, and as far as we know only Wilcap Company (805.481.7639) makes such a thing. However, you would still need to figure out motor mounts, cooling, exhaust, and more. In addition, many states require that when you do a repower on a vehicle that must pass smog, the engine must be the same year or newer than the vehicle it's going into. Many outfits such as Edelbrock (310.781.2222), Holley (270.781.9741), FAST (901.260.3278), and ACCEL (888.MR.GASKET) offer aftermarket fuel-injection systems.

Better advice is to sell that 440 and the complete Charger, then take the money and buy a late-model fuel-injected GM big-block that will most likely bolt in.

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