Help with Transfer case

[Chance Stanford]

Ok, im new to the site so I hope Im not doing anything bad by posting this as a new topic. I have a 1999 GMC sierra 1500 ext cab z71 4wd. I have gone through the transfer case 3 times and the noise is still there. If i take the front drive shaft out the noise is gone. When going down the road say 20mph and i put it in auto 4wd or 4 high i get this noise. However, I can make it go away by changing the throttle up or down. Like I can float the noise if that makes any since. This is a video of the truck jacked up and running in 4wd hi. Any ideas or suggestions? I can even here it very faintly in 2wd going down the road.

[worktruck2011]

I don't see a video, but the transfer case is noisy and makes a grinding sound whenever 4wd is engaged with the Silverado. I had to drive a few brand new trucks before I could believe that's just the way GM makes them.

[00Silverado4x4]

If the noise goes away with the front shaft removed it's entirely possible the front diff may be a problem area as well. However, if you can get the video loaded up then we may be able to assist you further.