Yeah my thinking was T case of viscous coupler. I have an over haul of the T case on my list, not sure if I will do the lower gear set or not. Be interested to hear if your bearings and gear upgrade has any effect on the noise.
I can't hear the noise for sure in your video. Mine makes a kind of grinding or growling sounds when I let off the gas, mostly noticable at speeds 50mph and under. Have not been able to track it down but it was there before I lifted the truck and is still doing it. It's been that way for the 7...