<strong>11. </strong>The Chase Series Super Duty kit comes with a set of mid-travel, mid-rate leaf springs. Our seven-leaf packs were built by Atlas Spring and were put under the truck with a 3-degree shim, to help pinion angles. There is no vibration from our rear driveshaft at high speeds. The new leaf springs give a much better ride than the factory leaf springs do, but do not have the load capacity of the stock springs.