Mmmmm, with your transmission in park and transfer in either high or low your single jacked front wheel won't turn anyhow, to check the centre diff jack said front wheel up and either put transfer in N or transmission in N, then rotate with centre diff unlocked. then locked, it should THEN turn freely unlocked and move marginally then stop when locked
Drop the oil and see what nasties lurk, this will usually tell you if your centre diff is RS
