This is the area in front of the rear tire. The upper and lower trailing arm mounts are both attached to this area. In order to reach the fastening hardware for the upper trailing arm mount, the factory put an access hole in the frame. Consequently, this introduced an area for large quantities of dirt, mud, road salt and moisture to enter the frame. Because there were no coinciding drain holes installed, everything collects inside, and creates a rust out condition, from the inside out. Because the upper trailing arm mount is located on the inside of the frame rail, it’s very difficult to see the corrosive process, before it’s too late. We also added a large drain hole, to help prevent a repeat problem in the future. Also, we’ve included new high grade upper and lower trailing arm mounting hardware to make your installation easier.