As easy as it is to double (or even triple) the power output of the modern diesel truck, that power is very hard on stock drivelines, suspensions, and axles. The most common side effect truck owners face once they begin adding power is rear axlewrap.
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What is Axlewrap?
When the engine’s torque load overcomes the rear suspension’s ability to keep the axle in place, the axlehousing tries to rotate in the opposite direction the wheels are turning (and literally twists the leaf springs into an S shape). When this happens, the differential also rotates, forcing the pinion gear to tilt upward. The result is a truck that suffers from wheelhop, driveline shake, driveshaft slip-spline wear, U-joint wear or failure, and even bouncing during transmission upshifts. With a load in the bed or a loaded trailer, even stock trucks can have damaging axlewrap due to the very nature of diesels: While under load, they make more power. On the other side of the coin, braking can also be detrimental. Heavy braking will cause the differential to rotate the other way, forcing the pinion angle downward. And hauling or towing a trailer amplifies the truck’s braking force and only makes the problem worse.
Problem Solved
The solution? Traction bars. While not as glamorous as a 300hp tune or a whizz-bang set of injector nozzles, traction bars are a vital piece of the power-making puzzle—and make your horsepower usable on the street, strip, or dirt. Built correctly, traction bars do not stop the axle from moving up and down during articulation and general suspension use, yet they do keep it from rotating back and forth. Because we needed a set on our ’97 F-350 after hitting the 400-rwhp mark, we contacted One Up Offroad for a set of its industry-leading, adjustable traction bars. Follow along as we install them, highlight their benefits, and tell you when you’ll need some on your truck.
Price List (for our ’97 F-350)
QTY:
Part:
Price:
2
Short-gusset, universal traction bars (kit includes two frame mounts)
$726
2
Bolt-on axle mounts
$299
4
¾-inch U-bolts
$147
Total Price
$1,172
One Up Offroad’s Traction Bar Benefits:
After making more than 400 hp at the wheels with our ’97 F-350 (“Serious 7.3L Upgrades,” August ’11), we installed One Up Offroad’s traction bars before returning to the dyno with even more horsepower on tap. The result was zero differential twist, no driveshaft plunge, and a truck that sat still on the rollers.<
- No more differential twist (pinion angle is said to only change 2 degrees at full suspension travel now)
- Controlled driveshaft plunge
- Improved launches at the track
- Both rear wheels remain grounded (equal ground pressure), providing constant forward progress and no rearend hop
- More suspension control—the leaf springs now stay where they’re supposed to
- Firmer transmission shifts (gear transitions are crisper and a lot of our F-350’s suspension flex during upshifts has been eliminated)
- Easier on driveline parts: U-joints, pinion yokes, driveshafts, and leaf springs
Work And Play
For Tow Rigs
You might recognize the One Up Offroad name from the off-road world. In the early ’90s, its traction bars were bred from the need to pull heavy trailers in soft sand dune areas, where wheelhop is common and tends to stop trucks dead in their tracks. The idea was to be able to tow and play in the loose sand—and do so in two-wheel drive. The ’00 F-250 shown here rides on 8 inches of lift, 37-inch tires, and tows a 32-foot, triple-axle toy hauler through the sand on a regular basis.
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For Lifted Trucks
As mentioned, One Up Offroad is well known in the off-road segment, and one reason is for making trucks equipped with its huge suspension lifts ride like stock. In particular, lifted ¾-ton and 1-ton trucks are where its CAD-designed (and simulated) components really shine. One of its best-selling products is its traction block system, which combines a strong, boxed-steel lift block with the traction bar. By eliminating the need for lifted trucks to run an add-a-leaf with this system, trucks equipped with it retain a factory-like ride and experience no takeoff shudder from the driveshaft.
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For Competition Vehicles
From sled pulling to drag racing, One Up Offroad’s traction bars are common in diesel motorsports—because they perform. We’ll use Aaron (Rudy) Rudolph’s record-setting 6.4L Power Stroke as an example: They give his F-250 drag truck the traction it needs to cut 1.47- to 1.60-second 60-foot times. The initial traction provided at launch often sends the 6,300-pound, Pro Street Super Duty well on its way to low 10 and high 9-second passes in the quarter-mile.
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