Have either of you guys ever owned an AWD/4WD vehicle before? What you are describing sounds like play in the U-joints. With AWD and 4WD cars there are a bunch of Universal Joints that allow the drivetrain to flex with the suspension. The noise you are describing, and the conditions, sounds like these joints shifting stress. Acceleration will put stress on the joints in one direction, and in the other when decelerating. During the transition the joint can make a *clunk* noise. It is very common, and nothing to worry about. However, there is a point when the joint bearings begin to wear, and you will experience lerching, and shudder, but with regular check-ups your mechanic will be ontop of the wear. BTW-Temperature does affect bearing lubricant, and cold weather will stiffen the joint. This will cause the *clunk" when driving over bumps as the joint flexes. I would take the truck in to the dealer, describe the issue, and have them check the joints. One also might not be tightened properly. This is a brand new car after all, and the manufacturing process still has some kinks. Otherwise, I would give it some time. Once the joints settle, the noise could subside a bit.