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Techline - Answers to all your 4x4 tech questions

Posted in How To: Tech Qa on May 10, 2016
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Photographers: Four Wheeler Archives

Shackle Angles
What is a good leaf spring shackle angle with full weight at rest? I'm building a flatfender Jeep with a spring-under rear suspension using Rubicon Express 4 1/2-inch-lift YJ springs to help control axlewrap. Up front I am using stock YJ leaf springs in a spring-over configuration. I had them set near 45 degrees, but when I flexed the suspension, my rear shackles flopped all the way back and got stuck on my bumper. I can cut up the bumper if that would fix the problem, but I wanted to get your take on proper angle and spring rate. It will be driven on- and off-road. What is a reasonable shackle length?

Also, I often see front CJ bumpers with round holes cut in them. Is it for increased air flow or something else?
Ryan Grenz
Via facebook.com/JohnCappa4x4

When building custom leaf spring mounts there are several things that you need to take into consideration. Centering the axle in the wheelwell with weight on the vehicle is the first step. As you have found, an arched leaf spring gets longer as it compresses and shorter as the suspension droops. This pushes or pulls the shackle and moves the axle away from the center of the wheelwell. The best way to get everything positioned properly is to mock up the spring and shackle mounts with a few tack welds and put weight on the suspension. It may take a few tries to get it perfect, but it will be worth the effort.

The angle at which you should set the leaf spring shackles will depend on the amount of arc in the leaf springs at droop, ride height, and compression. Heavily arched springs get significantly longer as they compress. You have to compensate for that movement. The more wheel travel you have, the more you need to take this into consideration. If the shackles bind up or lockout, you may bend or break the leaf springs. If your suspension has shackle bind or lockout, your setup will require the use of longer shackles. You may also need to rebuild the mounts to avoid altering the ride height via longer shackles. Some high-speed leaf spring desert setups have shackles that are up to a foot long. Of course, shackles like this need some sort of support to keep them from laying over sideways and bending. Fortunately, YJ lift springs won’t require this extreme of a shackle design. You will likely find that a resting angle of about 10 degrees will work for you, depending on shackle length. Like the shackle angle, the length of the shackles will depend on the length and arch of the spring and how it cycles. There is no set measurement that works everywhere. With the 4 1/2-inch YJ lift springs you are using, you'll likely want shackles that are at least 5-6 inches between the mounting holes, maybe longer in some cases. The use of a boomerang shackle can also help provide the clearance you need for the cycling suspension.

The holes you see in the front bumper of many older Jeeps can be done for several reasons. Airflow is only one reason for them. The holes are also made to lighten the front bumper, and in some cases, it’s purely for decoration. However, if you use a dimple die on the holes, you make the bumper more rigid. This allows the use of a thinner (lighter) bumper material, which saves much more weight than simply cutting the holes alone in a thick bumper. By itself, the weight savings of a lightened front bumper probably isn’t worth the effort. But if you apply similar lightweight tactics throughout your entire 4x4, the weight savings can add up. Companies such as Pro-Tools (pro-tools.com) and Swagg Off Road (swagoffroad.com) offer dimple dies in sets and individually.

Cummins Crisis
I have a ’98 Dodge truck with a 24-valve Cummins. It just turned 170,000 miles. I only tow with it and the check engine light is on. The engine starts right up when cold, but after the engine warms up, it won’t fire until it cools down again. It’s a hell of a way to travel, so I have been using two keys and let the engine idle when I make quick stops. Do you know what the problem is?
Chris Kilkenny
Via facebook.com/JohnCappa4x4

The hard-start problem you are having is more than likely caused by a failing injection pump. The ’98.5-’02 Dodge 24-valve Cummins trucks have the electronic VP44 pump, which generally won’t last as long as the mechanical injection pump found on the earlier Dodge 12-valve Cummins engines. You can install a new replacement pump using common hand tools. However, you will need the proper gear puller. Diesel Power Products (dieselpowerproducts.com) offers both stock and high-performance VP44 pumps, as well as an inexpensive gear puller needed for the installation. A new VP44 injection pump should be good for another 150,000 miles or so as long as you feed it clean fuel.

XJ Axle Swap Options
I'm about to start gathering parts for a two-door XJ build. It's two-wheel-drive and I'm building for 37-inch tires or maybe a little bigger. What axles would you suggest? I'm going the junkyard route for sure. Most of what I read says Dana 60s from a late ’70s Ford will work best. Any other axles worth looking into? I rockcrawl with a two-hour round-trip drive to the park. I want selectable lockers and 4.88 gears. Would used Jeep Rubicon Dana 44 axles work if I reinforce them?
Mark Fosbinder
Via facebook.com/JohnCappa4x4

Unfortunately, the days of finding cheap ready-to-run Dana 60 front axles are pretty much over. The fact of the matter is that not many ’70s 1-ton Ford trucks with a high-pinion Dana 60 front axle were built. And if you do find one, it’s likely pretty hammered and in need of lots of attention. Most used ’70s Ford Dana 60 front axles go for around $1,100, and they are nowhere near ready to run. You'll likely need new spindles, wheel bearings, kingpin rebuild kits, brake calipers, ring-and-pinion, install kit, axle U-joints, 35-spline stub axles, locking hubs, and so on. In many cases, it really doesn't make sense to rebuild a junkyard Dana 60, especially if it's bent or really worn out, neither of which is uncommon for a 40-year-old axlehousing. In my experience, by the time you add up the cost of parts and labor, you would be far better off with a brand-new Dynatrac (dynatrac.com) axle. The difference is that the Dynatrac axle will be made from all-new components and the housing will be much stronger than the Ford assembly. Plus, you won't have to do any of the cleaning or rebuilding.

If you are on a tight budget and you don’t plan to really wallop on the XJ, you might be able to get by with a Dana 44 front axle. Dana 44s are way more common and you can usually assemble a decent axle using wrecking yard parts. A ’80-or-newer Wide-Trac axle from an FSJ Cherokee or J-truck would be a good option for your XJ. The front axle from a J20 pickup will already have 8-lug hubs to match a 3/4- or 1-ton rear axle, although the more common FSJ 6-lug hubs can be converted to 5- or 8-lug with bolt-on parts. Around my neighborhood, I can find FSJ Dana 44 front axles for around $250.

The stock Rubicon Dana 44 axlehousings will be too light duty for what you have planned. The lockers and axle tubes don’t hold up all that well to tires larger than 35 inches in diameter.

The high-pinion Dana 44 frontend and Ford 9-inch rearend from a ’70s F-150 might also be a viable option. Although, if big rocks and a front locker are in your build plans, you should probably hold out for the Dana 60 front axle.

Another option is to go with ’99-’04 Ford Super Duty front and rear axles. The goofy 8-on-170mm metric lug pattern is a bit of a turn off, but there are plenty of aftermarket wheels available that fit. Also, I'm not a big fan of the Ford Sterling 10.50-inch rearend. In really abusive applications I have seen the axletubes break free and spin in the cast housing. Properly trussing the rear axlehousing will keep this from happening.

High-Test
I have a ’15 Jeep JK. Is there is any performance advantage in using 89 octane fuel in my Wrangler?
David
Via email

The simple answer is no: there isn’t a performance advantage when using 89 octane fuel in a Wrangler with a stock 3.6L Pentastar V-6 engine. Most factory engines are designed to run on regular unleaded fuel unless a higher grade of fuel is specified. The higher octane fuel in itself does not provide increased performance—it simply makes the fuel more stable. The 89, 91, 92, and higher octane fuels are designed for high-compression engines. Higher cylinder compression ratios and excess heat can make lower octane fuels detonate before the ignition spark fires. This results in knocking and pinging that can usually be heard by the human ear. It sounds like someone is rattling a glass jar full of marbles under the hood and usually occurs during acceleration or under heavy load. Advancing the timing, adding an aftermarket performance tuner, turbo, or supercharger will usually require the use of 91 octane fuel to achieve the full performance gain and avoid engine-damaging detonation.

Something to be more concerned about is the quality of fuel you are using. Some no-name gas stations supply generic fuels that don’t have the same detergents and additives as the name-brand fueling stations. The low-cost fuels can cause deposits to buildup in the injectors, on the valves, and in the cylinders. The cheapest fuel isn’t always the best for the long-term performance and reliability of your 4x4.

Off-Road Worthy Ranger
I have a ’90 Ford Ranger 4x4. It’s completely stock. I would love to add some stuff to make it more off-road worthy. I got stuck trying to help someone out of a ditch in the snow last year. I had to be saved by a Suzuki Samurai. I vow to not let that happen again, but I need parts. I have $1,500 I can throw into my old Ranger. What parts can I get that will adapt to my Ranger to make it more off-road worthy? It currently has all-terrain tires. Thank you for your time. Keep up the amazing work!
Edward Richardson
Sandston, VA

Building an off-road–worthy 4x4 on a budget isn’t all that difficult. Some of the best performance mods you can make are very affordable. I’d start by investing in a tire deflator and a quality air compressor for refilling the tires. Airing down your tires for off-road travel provides significantly more traction and flotation in the dirt, mud, snow, ice, sand and rocks. Aired down tires also provide a smoother ride off-road. Currie Enterprises (currieenterprises.com) and ARB (arbusa.com) both offer easy-to-use tire deflators with a built-in gauge. I’ve used a portable ARB air compressor (PN CKMP12) for several years now and have been pleased with the performance. The compressor is mounted neatly inside a small plastic toolbox, and the kit comes complete with a hose, fittings, and wiring that stow away in the toolbox as well. A hard-mount version is also available.

It’s likely that your Ford Ranger has open differentials front and rear. You might consider installing a rear locking differential to help get power to the ground. There are many different locking differentials available, however the Torq Masters (torqmasters.com) Aussie Locker and Powertrax (powertrax.com) Lock-Right lockers install easily into your factory open differential. No ring-and-pinion gear setup is required. These locking differentials will keep both rear tires spinning at the same speed when you apply power. In contrast, your open differential may only provide one-wheel peel in certain conditions, causing you to get stuck.

Lastly, you might consider adding an electric winch to your truck. There isn’t an abundance of winch mounts for an early Ford Ranger, but you may be able to modify and adapt something or even use a front-mounted hitch with a universal removable winch plate.

Airflow Tow
I have a ’99 K2500 Suburban with a 454ci V-8. I tow a 7,500-pound trailer. The combined weight is 15,000 pounds. I had to supercharge the big-block to 5 psi to keep up with the diesels. I also added mid-length headers and a MagnaFlow exhaust. I doubled the factory secondary transmission cooler size, and I added a 1,000hp radiator package from BeCool. It’s basically a stock aluminum radiator with aluminum tanks instead of plastic. It allows you to ditch the mechanical fan and add two 16-inch electric fans. The fans are rated somewhere around 1,925 cfm each. What is the cfm rating of my factory mechanical fan? Are these electric fans really going to support about 400 hp pulling 15,000 pounds up a 4 percent grade at 65 mph? Why 65 mph? Because that’s the sweet spot for the 454, right around 3,500 rpm. At 55 mph it comes out of Drive, down shifts into Second gear and the engine hits 4,200 rpm. At that point the check engine light comes on and the random misfire code is set. Ask me how I know. At least three times a year the light comes on while towing.
Chris Wrigley
La Crescenta, CA

You can’t really compare the cfm rating of an electric fan to that of a belt-driven fan. Most manufacturers of belt-driven fans don’t offer any cfm rating because it would be misleading. The cfm changes significantly as engine speed increases. Also, there isn’t a fixed shroud close to the fan blade like there is with all electric fans. At idle, a belt-driven fan isn’t moving much air, but at 4,000 engine rpm, it’s moving a lot.

Electric fans are a great way to free up a few horsepower and increase fuel economy in most applications. When set up properly, electric fans can also increase airflow over the radiator at slower speeds on the trail or in stop-and-go traffic. However, in extreme conditions, you are generally better off with a belt-driven fan. Your application would be considered an extreme case. First, you have to consider the increased power through the addition of a supercharger. Superchargers create heat while adding that power. Second, you’re pulling a heavy load, further taxing the cooling system.

If the new radiator actually added coolant capacity—and assuming that it is more efficient than the stock radiator—this will help some. However, you should ultimately stick with the factory, large belt-driven fan. You can also look at other ways to help get the heat out from under the hood with the use of hood louvers and vented inner wheelwells.

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