My son has been complaining about a mysterious rattle or clunk in the front end of his 96 4Runner when he hit the brakes or went around a corner. We isolated it to the antenna. I figured that a bolt had worked loose from the when we replaced his antenna mast. Turns out the bracket that supports the antenna motor was attached to the fender with one spot weld. The weld had turned loose. I was able to drill a hole in the bracket and the fender/body structure and insert a bolt. You need to remove the door threshold trim and the kick panel to get to where the bolt goes through the body sheet metal on the inside. I used a 10-32 bolt and self locking nut with the bolt head on the inside. Had to remove the plastic fender flares and the plastic trim on the front of the running board. Also need to cut about 6 of the plastic fasteners that hold the inner fender in place to get access to the antenna motor and bracket.

Had not heard of this problem before. Maybe this will help someone find that strange noise in the front end.