This procedure applies only to trucks. Turn off the air suspension system. Loosen rear wheel lug nuts, raise rear of vehicle and support securely on jackstands. Remove rear wheels. Support axle with floor jack and raise slightly to relieve tension on leaf springs. Remove U-bolt nuts, spring plate, rear spring spacer (4WD models only), and U-bolts. Lower floor jack to unload spring. Remove nut and bolt from spring-to-front bracket. Remove upper spring-to-shackle nut and bolt. Remove spring assembly. Replace worn or deteriorated bushings. Installation is reverse of removal. Gradually tighten U-bolt nuts in criss-cross pattern. Tighten all fasteners. Lower vehicle. Reactivate air suspension system, if equipped. Turn off air suspension system. Loosen rear wheel lug nuts, raise rear of vehicle and support securely on jackstands. Remove rear wheels. Support axle with floor jack and raise slightly to relieve tension on leaf springs. Disconnect air line from solenoid valve. Unplug electrical connector from solenoid valve. Remove retaining clip from top of air spring. Compress air spring and remove. Installation is reverse of removal. Lower vehicle and reactivate air suspension system. Start engine and allow compressor to fill air suspension system. Do NOT drive vehicle until air suspension system has been restored.