My 09 3500 4x4 duramax under moderate to hard acceleration has a vibration/chatter in the drive line/entire truck. Feels like running over rumble strips on the road. When in 4 high it's worse. When the truck is in 2 high and pulling a loaded trailer the chatter is horrible. Also when switching in to 4 high while driving I can feel a mild vibration when mild acceleration or deceleration is applied. The truck is stock except for leveling kit and some 295's. I have check the drive line for slack, drive shaft, cv joints.....I am out of suggestions the truck has only 13000 miles on it. Please Help.