I pulled the filler plug on the transfer case and drained just over 2 quarts out. It was plumb full. I have been occasionally adding trans fluid for probably over a year and wondering where it was going. I found the answer. Doesn't seem like that could make a transfer case go to 4WD by itself but, it certainly is a coincidence.
Think of this as a hydro lock of sorts. This transsfer case has bypass passages from trans to TC. Best person to confirm this is BP, our resident trans specialist, but he is MIA lately, probably has better things to do in life such as life.
I think I wrote at first here that we need some form of communication. If we acsertain TC module is functioning, what else can there be apart from an over-pressure. If putting fluid levels back to normal did not fix it, you are barking up the wrong 4x4 symptom and need to regroup and come back with how it is now, once everything level.