Almost screwed up my new truck. Was backing out of the garage and did not realize the door did not go all the way up. When all of a sudden I here the crunch sound. The onstar antenna had caught the rubber bottom of the garage door. it tore a little section of the door bottom but the antenna is ok except it seems a little loose. Looking at it, i cant seem to find out how it comes off so I can check it out and tighten it. There is a seal slot near the bottom that must somehow release it front the mounting bracket. Does anyone know how this comes off?