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Ford Super Duty Suspension - Playing The Odds

We Test Pro Comp's Double XX Super Duty 8-Inch Dual Coilover Kit.

Photography by Robin Stover
  • 10. This shot shows Pro Comp's bolt-on rear traction bars, which help combat torque shudder commonly found in Power Stroke-equipped Super Duty pickups. One thing we really liked about this traction bar is that the axle end mounts between the axle spring plate and lift block, causing no loss of ground clearance, which has been a drawback with other traction bars we've seen in the past. With polyurethane bushings at each end, this traction bar should do a fine job at twisting enough so that axle movement isn't limited.
    10. This shot shows Pro Comp's bolt-on rear traction bars, which help combat torque shudde
  • 11. After leaving Pro Comp's Chula Vista, California, headquarters we stopped by Pro Comp Tire and Wheel in Compton, California, to get our project a new set of shoes. The good folks of 4Wheel Parts in Redondo Beach, California, gladly installed four brand-new 37x13.50/17 Xtreme All Terrain tires on a set of Pro Comp's new 17-inch rotary-forged aluminum alloy wheels in a matter of minutes.
    11. After leaving Pro Comp's Chula Vista, California, headquarters we stopped by Pro Comp
  • 12. We had the new tire-and-wheel package weighed on a digital scale to see how much additional rolling mass we were about to add to the truck. We were surprised to see each wheel/tire come in at 116 pounds, not bad for this combination.
    12. We had the new tire-and-wheel package weighed on a digital scale to see how much addit

13. Once the new tires and wheels were mounted, we drove the truck around Los Angeles for a few days to get a feel for the new suspension system. While we loved the new smooth ride afforded by the kit, we found that the larger tires made slow, tight maneuvers in parking lots almost impossible. With worn-out arm muscles, we called Pro Comp to find out why this was. They told us that we probably had a Super Duty that came from the factory with a finicky steering box. "Some have no problem steering 37s, while others simply make it impossible," said Jeff Blakely of Pro Comp Suspension. To resolve this issue, we stopped by Off Road Unlimited (ORU) in Burbank, California, to have one of its killer ram-assist steering systems installed. ORU's ram-assist kits are, simply put, the best thing you can do to resolve the stiff Ford steering-box issue. In about six hours, we had steering that felt more like an Acura sedan than a 1/2-ton truck. Keep in mind that not all Super Duty pickups will need this modification, and that not everyone has puny little toothpick arms like the author of this story. But, should your truck steer much harder after a lift and bigger tires are installed, the solution is simply a phone call away thanks to ORU.

14. We tooled down the highway, happy as clams with the truck's new ride and steering feel. However, now we noticed that the speedometer was incorrect and that the truck seemed to lack power off the line. So we called our friends at Right Gear and Axle of Salinas, California. Right Gear and Axle specializes in gear swaps and drivetrain overhauls. They concluded that we should swap out the stock 3.73:1 axle gearing in favor of a lower 4.33:1 ratio. While we were at it, they suggested we also remove the OE limited-slip rear differential because, at 36,000 miles, it was probably not working anymore. A simple jackstand test confirmed this. We had the guys at Right Gear replace the non-functioning factory limited-slip with a Detroit Truetrac unit. Our buddies at Eaton/Detroit told us this was a very common swap, as the clutch-style limited-slips wear out quickly under the torque loads of the Power Stroke engine. The best part about a Truetrac, which uses helical gears, is that there are no clutches to wear out, and the units themselves are pretty much indestructible, unlike other limited-slips that use clutch plates and springs.

  • 15. Here you can see one of the mechanics from Right Gear and Axle replacing the factory rear differential with a new Truetrac unit from Eaton. We were impressed with how quickly these guys got our gear swap done, leaving all afternoon for a photo shoot.
    15. Here you can see one of the mechanics from Right Gear and Axle replacing the factory r
  • Before
    27 inches was all she took to lift a rear tire.
  • After
    36 inches, a vertical gain in articulation of 9 inches.

With just over 25,000 miles on the Double XX kit, we decided to take it back to Pro Comp for a check-up. They were blown away that our testdriver was able to rack up so many miles in just over six months' time. We hadn't noticed any major issues with the kit, and the single-shear lower shock mounts seemed to be doing just fine. After a quick retorque session, they did discover that one of the front 2.75-inch shocks was weeping oil from a shaft seal. They told us that this was likely due to our shocks being assembled prior to actual production parts, but in any case the entire shock was replaced to allow Pro Comp's R&D department a chance to evaluate what went wrong. A simple seal failure was the culprit.

Next, we discovered that one of the rear-axle lower shock mounts was moving slightly from its intended position. This alarmed us at first, but then Pro Comp replaced this bracket with a brand-new one and instructed us to have each side of the bracket welded to the axletube to prevent further movement. We had this performed and haven't had a problem since. Keep in mind that our tester is very hard on his truck, jumping it any chance he gets, and in most cases is a lot harder than the average consumer would be. Pro Comp agreed with us that in most cases, the rear shock mount issue wouldn't happen at all.

A high-end suspension system like the Double XX kit allows for increased speed and mobility over all kinds of harsh terrain. We did a little testing with this kit down in Baja, Mexico, last year. Though the suspension system performed well in just about every environment, we did find one place where it gave our testdriver way too much confidence, allowing him to overdrive the factory headlights at night. It happened on a road we call "one of the worst roads in Baja," between the small fishing village of Puertecitos, about 100 miles south of San Felipe on the Sea of Cortez side, and Gonzaga Bay, another great fishing spot. This road is the type where suspension systems will make or break your trip. During the day, with a good suspension system, you can drive 60 mph easily, slowing only for the occasional washout, hard corner, or stray cow blocking one's path. At night, however, it's quite a different story, and speeds of 40 mph are flat-out dangerous with only factory headlights. Our tester installed these lights and headed south after the Baja 1000 last year, and found that the increased field of view afforded by the new HIDs, in conjunction with the Double XX kit, allowed him the ability to cruise through the darkness at speeds typical of a sunny day. These 9-inch HID lights are sold individually, and each comes with a clear, polycarbonate lens protector, built-in ballast, and a heavy-duty aluminum adjustable mounting bracket. The killer part about these lights is that each puts out more light than a standard 9-inch, 130-watt halogen type light, but only uses 2.9 amps of power, so your electrical system doesn't get zapped while 'wheeling at night.

SOURCES
Eaton
8-00/-328-3850
eatonperformance.com
Pro Comp Suspension
4 Wheel Parts of Redondo Beach, CA
www.4wheelpartsstores.com
Pro Comp Tire and Wheel
Off Road Unlimited
www.offroadunlimited.com
Right Gear and Axle
www.rightgear.com
Precision Gear
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