Hi all.. I just joined and this is my first issue so here goes. I just purchased a 2000 Yukon ( 5.3 motor) . After parking the vehicle after being driven I hear a single "pop" or "bang" coming from the rear.This noise happens minutes after shutting off the truck. It sound sort of like like a pop bottle expanding. I have had the truck for a week and have heard it at least once a day.