If you have recently bought a new single-axle utility trailer kit, you may need to connect the axle to the trailer frame. The typical utility trailer is mounted to a single axle, suspended by leaf springs at either end. The leaf spring design protects the axle, and your cargo, from damage. Without the leaf springs' ductility, the axle would quickly wear, become misaligned and pose a safety concern during travel. Once you have installed the axle and leaf spring assembly, check that the axle is aligned perpendicular to the trailer tongue.
Jack up your trailer frame. Support all four corners on jack stands or blocks.
Locate the front and rear shackle hangers along either side of the trailer frame. Fasten one end of each leaf spring to a front shackle hanger with a bolt and socket wrench. Allow the leaf springs to hang down.
Place the axle across the centers of the leaf springs. Raising one leaf spring at a time, attach the free end of each leaf spring to a rear shackle hanger on the trailer with bolts and a socket wrench. The axle should be suspended in the air across the leaf springs.
Secure both ends of the axle to the center of each leaf spring with a U-bolt, retainer bracket and socket wrench.
Tighten all the bolts to the manufacturer's torque specifications with a torque wrench. Remove the jack stands or blocks and lower the trailer.
Check the axle's alignment by comparing the distances from the center of either wheel to the tip of the trailer tongue. The distances should be within 1/8 inch of one another.
