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Project F-150, Part IV - Off-Road Magazine

Posted in How To on April 19, 2006
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In our last installment, we installed King's new F-150 coilovers and reservoir shocks along with 34-inch Goodyear AT/S tires on American Racing RT-S alloy wheels. The suspension works great, but the larger tires really affected the performance of the F-150. At 3,300 feet altitude, with stock tires and gearing (with the truck cap and bedliner installed), our F-150 went 0 to 60 mph in a leisurely 9.1 seconds. With the larger tires and wheels installed and the stock 3.73s unchanged, the truck now turned in a poky 10.5-second 0-to-60 time. We needed to change the gearing and add some horsepower.

St. George Ford is southern Utah's largest Ford dealer and is a Roush dealership as well. Its giant service department is excellent.

After much debate, we decided to go with 4.10 gears that, with the 34-inch-diameter tires, would return us to stock gearing. We liked the stock gearing when we had the stock tires, both on the highway and off, so this would do. We contacted West Coast Differentials and ordered gears for our 8.8 reverse frontend and Ford 9.75-inch rearend. We also plan on taking this off-road, so we wanted some kind of traction-adding differentials front and rear. Since this is our daily driver, and there are no plans to take the F-150 rockcrawling, we decided on a pair of strong Detroit Truetracs, the only differential currently available to the aftermarket featuring a gear-type limited-slip design (there are no clutch or friction plates to wear out). The Truetrac's positive gear action provides quiet, automatic splitting of torque. Bruce Alldridge, the gear expert at St. George Ford in St. George, Utah, installed the gears and Truetracs quickly and perfectly. There's no gear whine or clunks in this F-150.

For power, there are many ways to go. We didn't want to void our factory warranty though, so our choices were narrowed to one - a ROUSHcharger. The Roush F-150 5.4L 3V supercharger kit includes everything you need for a bolt-on installation and affords gains of up to 112 hp and 112 lb-ft of torque with 6-psi boost. Roush says the kit installs in about eight hours, but Rocky Schmalz at St. George Ford only took six to complete the job (after receiving the ECM back from Roush). Of course, he had done a few F-150 supercharger installations before. Roush now offers an intercooled version of its ROUSHcharger that adds even more performance. We're happy with what we got with the nonintercooled version. If your F-150 is still in the 3-year/36,000-mile factory warranty period, the supercharger is covered, as are all driveline components affected by it, for the balance of the warranty. If your truck is out of warranty, all Roush parts are warranted for a full year.

Remember our poky 10.5-second 0-to-60 time? On the way home from the Ford dealership after the Roush supercharger and gear installation, we ran a couple of timed 3,300-foot-altitude 0-to-60s and found we could now get to 60 mph in 7.6 seconds. For those of you who scoff at our 7.6-second time, remember we're driving a heavy fullsize truck, with a truck cap and wheel/tire combos that weigh 95 pounds each.

Follow along and we'll show you how easily Rocky performed the supercharger installation. A warning though - don't use this feature as your instructions. We want to show you what was involved to install the ROUSHcharger, but space precludes us from showing every detail here. In other words, we left some steps out. If you get a ROUSHcharger of your very own (highly recommended), read the instructions that come with it and follow them carefully!

PhotosView Slideshow
PhotosView Slideshow


West Coast Differentials
Rancho Cordova, CA 95742
Eaton/Detroit Locker

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