SuperPro KIT168SK Rear Greasable Pin, Shackle and Bushing KitSuperPro KIT168SK Rear Greasable Pin, Shackle and Bushing Kit The Rear Spring Shackles and Fixed Pins are often overlooked when upgrading the suspension of a 4WD. Original shackles and fixed pins corrode and destroy the bushings and it is the leaf spring bushings that stabilize the movement of the rear axle. Worn or inferior bushes in this area will cause the solid rear axle to move and impart rear end passive steer to the vehicle leading to the