Update!
Did a transmission flush and reconnected the front driveshaft. Badness ensues.
On the highway under acceleration I will occasionally hear a loud bang come from the transfer case. When this happens, the TOD lights for the front wheels light up at full torque for just a moment. I take this as being indicative that I have a chain that's hopping.
I have found zero information on parts needed for a chain replacement, and the workshop manual makes the job seem at least a little daunting. It appears the easiest solution at the moment will be to find a TOD t-case from a 98-05 Trooper.