1500hd thumping noise from 40+ mph

[painkiller]

i have a 2003 1500hd gmc sierra, i have had the intermead shaft replaced before, i developed a thump thump thumping noise a few weeks back , it starts around 40 mph and gets faster as the mph's go up.when i apply the brakes while still on the gas it seems to stop, or when i turn a curve. i have greased the intermead shaft all joints, checked brakes , fluids , u joints. i am about to decide that it must be a wheel brg but not sure. what are the sensors on the wheel brgs? has any one else had this prob? this truck has not been abused . thanks Bill