DDT = Detroit True Trac differentialwhats a ddt ? i am not positive but it def feels like something in the drivetrain .a few times it actually nudged forward a little if my foot was on the brake lightly . i was told its something with the 33 gal gas tanks that i could understand if you came to an abrupt stop and the gas swooshed back and forth but this happens after i am stopped for a while at a light .