Adding Bypass Shocks to Our Solid-Axle F-150
Making an Old Ford Go Fast
Over years we have upgraded our 1977 Ford F-150 with a 460 engine from LA Speed, an Offroad Design Doubler, and Super Duty axles with Detroit Locker and Sierra gears. All of that combined to make a truck that was reliable on the street and capable on the trail, but limited to low-speed crawling. While we had plenty of engine to go fast, the single 2-inch shock at each corner took issue with having to control the 6,900-pound truck during spirited driving off-road. To resolve this issue, we installed some used 3-inch bypass shocks that we were able to pick up at a fraction of their retail price.
We should note that this is not the correct sequence of events if you want to maximize wheel travel. The right thing to do would be to remove the front coil springs, determine how much uptravel you have before suspension components start crashing into each other, and measure how much droop you have before the driveline or suspension binds. Similarly, in the rear you would remove all but the main leaf of the springs and cycle the suspension to full bump and full droop. The next step would be to order shocks of the appropriate length. That is expensive though.
Instead we took the 10-inch-travel bypass shocks we purchased used to Rock Hound Off Road in Auburn, California, and had them build custom mounts front and rear. Rock Hound set up the shocks in the middle of the travel to utilize the bypass tubes as the suspension cycles. They then built bumpstop mounts to prevent the shocks from bottoming and added limit straps to keep the shocks from over extending. While we left some suspension travel on the table by approaching things this way, the price made it worthwhile. And with 42-inch tires, low gears, and Detroit Lockers, we don't have to worry too much about articulation to get through most trails.
So why go through all the trouble? The larger-diameter shocks allow for a larger piston and shims, which provide more precise velocity-dependent valving. They also hold a larger volume of shock oil to prevent fading during continued use, and they are completely rebuildable and customizable. The bypass tubes allow for further customization by making the shock valving position-dependent in addition to being velocity-dependent. As the name suggests, these tubes allow oil to bypass the shock piston in a certain zone of the shock.
Of course, all of this adjustment means that there's just as much potential to get things wrong as right. Our used front shocks came off of a sand truck with a small-block engine and leaf springs, and our rear shocks were for a Ford Raptor, so both ends needed to be revalved and fine-tuned for our heavy Ford. Samco Fabrication has years of experience tuning the suspension on championship-winning desert race trucks, including stock class vehicles that have the same limited amount of suspension travel as our Ford. After riding in our truck over a test loop, Samco was able to adjust the compression and rebound tubes on our shocks to make it ride smoothly over washboard while still withstanding larger hits without bottoming out.
Considering that we did not change our radius arms, coil springs, or rear leaf springs, the improvement in ride quality that was achieved just through the use of new shocks was astonishing. The truck rides better on the street now with more rebound damping to control the heavy engine, 16,500-pound winch, and pipe bumper hanging off the front end. In rockcrawling the difference is negligible, but as speeds increase on the trail so does the difference in performance, making our old Ford a well-rounded vehicle for nearly any terrain.