Vibration/chatter under hard acceleration

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.:help2:

Dealer time maybe? No way they can claim your tires and leveling kit are doing this, sounds like an improperly balanced driveshaft to me. In 4HI its worse, hmmm wonder if there's an issue with the front driveshaft?

kinda what I was thinking.....thanks for the input