How to repair a horse trailer
Raise the trailer with a jack and support it on a set of jack stands. Remove the old springs if they are still on the trailer.
Place the spring under the trailer axle and slide the eyelet of the spring into the front spring hanger. Install the retaining bolt through the hanger and leaf spring eye, and loosely attach the nut on the bolt.
Lift the spring, slide the rear spring eye into the rear hanger and install the retaining bolt. Install the nut on the bolt, but do not tighten it yet.
Install the U-bolts around the axle and assemble the spring plate onto the U-bolt. Loosely attach the nuts onto the U-bolts. Tighten the nuts with a ratchet and deep socket, working in an "X" pattern and tightening the nuts evenly.
Tighten the front and rear spring hanger bolts using a deep socket and ratchet on the nut and a wrench to hold the bolt. The bolts need to be tight, but do not tighten them so much that the spring can't pivot in the hanger.
Move to the opposite side of the trailer and repeat the process. You can now install the wheels and tires on the trailer, and remove it from the jack stands.
Things you may need to change it out: