I reread the thread again and if I understand correctly....the wheels/hubs only get hot with it in 4wd and/or the hubs locked in, right? If the hubs are not turned to "lock" or the tcase is not in 4wd, then the wheels/hubs do not get hot, right?
If that is the case, then it sounds like a problen with where the axleshaft comes through the spindle. Like wildgoody said, there is a brass bushing inside the spindle. If, for some reason, there is no grease on that bushing, then it is possible that the axleshaft is grinding against that bushing and causing things to heat up.