Transfer case Problems? Diagnoses

[4Motion4g63]

OK well I have some noises and they sound like there coming from the center of my car...

They are a "Growling chatter" or "Deep Buzzing chatter" after I lift off the gas and decelerate with the car in any gear, If it is out of gear it stops or when you get back on the gas.

I suspect the transfer case, but I have changed one to another used one and have the Identical noise, I also have checked the driveshaft and all looks good, even the carrier bearings are in great shape..

What Else could be causing this noise? I have also swapped to a 4 bolt rear end at the same time as the front transfer case...
The noise was present all the time before and after the swaps...

 

[4Motion4g63]

Update for this thread......I have installed another transfer case and found the Identical Noise...

I also have found that my Motor mounts are SHOT and the motor is binding the drive shaft and transfer when i lift and un binding when i push on the gas.... Figured it out but have yet to correct it so NOT 100% sure its it but It seams to be the culprit...