Typically the travel cycle of the Super Duty rear axle is an arch.
Our Traction Bars are designed to reduce rear leaf spring axle wrap caused by lift blocks and oversized tires. Track Bar Bracket;Rear;For Use w/Fabtech Rear Leaf Springs Or AMP Steps;California Residents: WARNING Fabtech Track Bar Bracket - FTS92025 This provides a non-binding, smooth highway ride, while still providing positive resistance to torque loads, reducing axle wrap and increasing tire traction.