I have a 2000 extended cab Z71 and it has a Fabtech 6" suspension lift on it, and when I come to a stop and take off again it makes a sound like its rubbing or the leaf springs are moving or somethin, I tightned the U bolts down and it's still doing it, I need help or is there a kit to make the axle stop from moving? thats what it feels like and sounds like to me?  thanks I need help---  

Since you have a large lift and likely very large tires what is happening is that the axle is wrapping up in the springs from the torque needed to launch the truck. If you have spacer blocks it can really aggravate the problem even more. The only cure is a stiffer spring pack and removing or reducing the size of the spacer blocks or go to a high dollar 4 link coil over setup which would control axle torque wrapup. If you still have stock gears it is not helping either because the extra drive shaft torque required twists chassis and springs on a axis perpendicular to drive shaft axis  (there are to forces to control the twist against the tires and the reaction to drive shaft torque) Lift kits do not take this into consideration nor do most that lift trucks consider the possible effects of higher drive line torque with big tires and stock gears. With a 6 inch lift and 36 or so and stock gears in is kinda like you are towing a 2000 to 3000 lbs trailer all the time with stock tires as far as drive line is concerned because it has to deal with a lot higher average torque in daily driving. This is one reason why you regear truck with over sized tires because you cannot chip or tune this problem away.  

Sounds like you are hearing your leaf spring bushings. Axle wrap sucks, but it is a way of life unfortunatly. An aftermarket spring pack that will eliminate the blocks will help tremendously, or a set of traction bars.