Important: Do not straighten the axle housing in order to correct an alignment problem. If the rear axle housing is not straight, the rear axle housing must be replaced.
If rear tire wear indicates that the rear axle housing may be bent, or that the rear springs may be dislocated, check the alignment.
You cannot align the rear wheels by regular means. Replace any bent or damaged components. Often the frame will not be straight. This can be verified with 3 dimensional measuring equipment. You can straighten the frame using frame straightening equipment.