Most trailers that are constructed for consumer use have tubular steel axles. They are easily bent during an uncontrolled skid or collision. Fortunately, replacing the axle is not necessary unless it is extensively damaged. With welding skills and attention to detail, axle repair is possible. It is, however, important to weld the axle after straightening it in a step-by-step manner to prevent the axle from warping. Repairing less durable, square-tube axles is not recommended.
Jack up the trailer and support the trailer bed with jack stands. Remove the tires and loosen the U-bolts with a socket wrench. These bolts hold the axle to the shackle springs. Once removed, lower the axle and support it on two additional jack stands.
Lay an 8-foot level on the axle and locate the low area where the impact occurred. This indent is the point of stress created during the impact. Rotate the axle, spinning it several times, and take precise readings with the level. Be certain that the point of impact is correct. Place a mark with the chalk on this point.
Rotate the axle 180 degrees (opposite) the mark on the impact site. This is the "bulging" side of the bend. With a grinder that has a thin, metal-cutting blade, cut into the bulge, going halfway around the axle. Lay a hardwood block on the cut and use a heavy shop hammer to drive the cut closed. This takes several sharp blows to accomplish. Continually use the level to ensure that the axle is straight.
Tack-weld the closed cut in several places with a wire-feed welder. (The axle will not shrink, recreating a bend.) Allow the tack welds to cool. Reconfirm that the axle is straight by using the level on all points around the axle. Make any modifications as needed before welding the cut completely closed.
Weld the cut closed when the level readings are good. Finish the weld by grinding the metal smooth. Spray a durable, black paint that will withstand the elements. This step will prevent rust formations on the axle repair.