The parking brake, if like the Nitro, consists of 2 skinny shoes inside of the rear rotors. Like the old drum brakes. Debris is known to get in there or rust can build up on the shoes if you never use the parking brake. Engage your parking brake slightly, to the point of the shoes engaging the rotors, and drive a short distance. See what happens. I have had my DJ since last June and have never once used my parking brake.