I recently picked up a 03 4.7 4WD Z71 and it is making a horrible grinding / crunching noise. You can hear it in the videos below. With the front end jacked up the front wheels spin freely with minimal/normal brake noise/drag. The front wheels have no movement that would lead me to believe it's a hub issue. With the truck fully on stands the noise starts immediately.
Not sure if it matters but the owner I bought it from pulled the front drive shaft because the "U joints went bad and I didn't have a press to fix it so I pulled the front shaft."

First link is the truck front wheels on ramps and rear axle on stands.


Any help is greatly appreciated.

 

gm makes a 4.8L
if the noise is occuring with the rear end on stands and the front stationary...it rules out the front dshaft (it doesn't turn in 2wd)and everything from the front ie hubs, axles differential. focus on the rear driveshaft, tcase, rear diff and rear axles.