Ring/rattle In Front End When Driving

[Paxonator]

I've asked a few mechanics around and they're not sure what the problem is. When I drive 50kmh+ you can hear a ring/rattle coming from the front end of the truck. Here's what I know:

 

Truck: 2002 Sierra 1500 sle 4x4 z71

 

1. If I put the truck in 4x4 and hit the gas the noise is gone.

2. You cannot free spin the front drive shaft when in 2x4.

3. We had it up on the hoist and in 4x4 the front drive shaft was clanking around but we weren't sure if that was from not having any tension on it from being off the ground.

4. We spun each tire and no noises were heard

5. The front drive shaft spun in 2x4 on the hoist (the tires did not)

 

The suggestions I got were to remove the front drive shaft (which i think i can do myself) and see if the noise is still there. Also to check U Joints.

 

Any help would be greatly appreciated!

[Paxonator]

Well I took the front drive shaft off went for a drive, and the noise is gone. you can spin the front differential without the drive shaft on. U joints are good. Asked the mechanic and he doesn't know. Only suggestion was to get my transfer case serviced to see if there's anything unusual going on in there.