2017-20 Ford F250/F350 4WD. Reduce rear leaf spring axle wrap caused by tall lift blocks, heavy torque engines and oversized tires with Fabtech's heavy duty Traction Bars. These Traction Bars utilize a shackle design on one end to allow movement with the arch of the leaf spring travel. This provides a non binding, smooth highway ride yet still provides positive resistance to torque loads. These floating style Traction Bars are a bolt on design for easy installation. Floating Rear Traction Bar System.