[DurangoPaul]

In park, there's nothing moving inside the transfer case, I think the noise may be carrying from somewhere else.

 

[DurangoPaul]

The t/case is chain driven between the input and output to the front driveshaft. The chain could have stretched enough to be rattling in the case. Not an uncommon happening. Usually not noticed until the case comes apart, either for maintenance or because it blew out.

That makes sense! I'm going in in a couple of weeks for the install of the new tranny pan & rear diff cover. I'll have it looked at then?Thanks, Mike!

I was going to suggest that the chain has stretched and that eventually it'll slap the case, but then I realized that he stated "while in park" so there's no torque being applied to the Tcase input shaft, and if it's not moving, there's no torque being applied to the output shaft by the driveshaft, therefore nothing inside the Tcase should be moving. Has to be something else.