rattle/vibration under throttle
 

I have an 07 Sierra classic, put on a 6 in lift and 35's. My problem is under acceleration, if I hit a bump I get a bad vibration, clunking noise from the rear area of the truck. The noise will ramain until I let off the throttle, and with come back if I hit another bump. Let off the throttle it goes away. Any help would be appreciated. It has 21,000 miles, and is still virtually a new pick up. Thanks.

I don't know much about this area but I would bet it has something to do with the change in the angle of your driveshaft. Good luck.

Have that driveshaft checked for a loose bolt or bad joints.