Well it is the 2.2 5 speed, and it is coming from the right side about where the passenger door is. I got under the Truck last night and I heard it while the vehicle was at idle. as the truck heated up and the idle smoothed out it went away. I am going to check again, someone else suggested a heat shield, but I didnt see anything like that. I heard it again when I was driving to work this morning, when the truck warmed up. I didnt hear it initially, when the truck was cold, but as the tem got warmer, the rattling came back. It is more prevalent on initial takeoff and then after 2nd or 3rd is no longer audible.