SuperPro SPF2155K Front Spring Shackle Upper Bushing KitSuperPro SPF2155K Front Spring Shackle Upper Bushing Kit These bushings are often overlooked when upgrading the suspension of a 4WD. Leaf spring bushings stabilize the movement of the rear axle. Inferior, worn or damaged bushings in this area will cause the solid rear axle to move and impart rear end passive steer to the vehicle. It also causes the vehicle to "wander" all over the road and be unstable under heavy braking. This can be especially