Rear leaf spring shackles are commonly used to “Level” trucks. For those of you who just can’t stand the “stink bug” look of factory stances, the lowering shackle is for you! Typical drop is two inches and fairly simple to install. You simply remove the factory shackle and replace it with a longer drop shackle. Be sure to use the one designed for your particular truck!
The leaf spring shackle is located on the rear of the leaf spring and is the only part of the rear suspension that is designed to move. When you hit bumps and dips, which cause the rear end to move up and down the leaf spring actually gets longer and shorter relative to the frame. It is the shackle that pivots forward and back with the leaf spring while being firmly attached to the frame. A good tip when installing shackles is to lubricate the bushings and bolts and be careful to not overtighten. It is possible to tighten so much that the shackle will not pivot, which can cause the truck to ride horribly, and affect ride height. Of course you the pivot bolt needs to be tight and you should use the factory locknut, just don’t set your pneumatic wrench to kill and run it down until it stops.
Correctly referred to as spring eye hangers, this is the bracket that secures the front of the leaf spring to the frame. There is no movement here, this is a fixed mount. There is a little movement in the leaf spring bushings as the shackle pivots back and forth so it is still a good idea to apply a little lubricant to the leaf spring bushings and not overtighten. The typical drop is two inches but some applications have multiple settings so you may adjust the amount of drop to better suit your needs. This part is rarely used by itself to lower, primarily because of the labor to install, but is teamed up with shackles to complete “Hanger & Shackle” kits, which are very popular for mild drops. The range of drop for this type of kit is three to five inches depending on the application.