To remove the left leaf spring on a 1500 model or either spring on a 3500 Cab-and-chassis model with an auxiliary fuel tank, first relieve the fuel system pressure. Loosen the rear wheel lug nuts, raise the rear of the vehicle, and support it securely on jackstands placed under the frame rails, blocking the front wheels to prevent rolling. Remove the rear wheels and the trailer hitch if equipped. For the left leaf spring on a 1500 model, remove the fuel tank; on 3500 models, the auxiliary fuel tank must be removed to access the rear shackle bolts. If removing the right leaf spring, unbolt the rear portion of the exhaust system from the flange forward of the muffler and detach it from its rubber hangers for clearance. Support the axle with a floor jack and raise it slightly to take the weight. Remove the four U-bolt nuts and washers, then take off the spring plate and U-bolts, discarding the old U-bolts and nuts as new ones are recommended for installation. At the front end of the spring, remove the nut and bolt from the spring-to-front bracket, and at the rear end, remove the spring shackle-to-frame nut and bolt, noting that the shackle-to-spring nut and bolt cannot be removed until the spring and shackle are detached from the vehicle. Lower the jack slightly to remove the spring assembly, and if necessary, detach the shackle from the spring and remove the U-bolt top plate and spring spacer if equipped. If the bushings at the ends of the spring are worn, an automotive machine shop or dealer service department can press out the old ones and press in new ones. For installation, if removed, attach the shackle to the spring without tightening the nut yet. Position the spring and install the forward mounting bolt and nut, again without tightening. Raise the axle until it aligns with the spring, then install the spring plate and new U-bolts, securing them with nuts and washers, and tighten the U-bolt nuts to the specified torque. Finally, tighten the front mounting bolt/nut, the shackle-to-frame bolt/nut, and the spring-to-shackle bolt/nut to the specified torque, then reinstall the wheel and lug nuts, lower the vehicle, and tighten the lug nuts to the specified torque.