2003 Chevy Silverado Noise and lag during first to 2nd gear

I have a Z71 four wheel drive P/U and it feels like when the truck is shifting from 1st to 2nd gears (Auto Trans) that there is a lag in drive take up a small audible noise is heard but not back but there is a lag in the tak up. Could this be a trans problem, worn carier bearing, or worn rear end gear. This is while in rear wheel drive , I have not tried it in 4 wheel drive.