I have a new to me f250 4x4 7.3 truck with 234K miles on it. I went to put it in 4 wheel drive this week end and it stayed in 2 wheel drive even though the dash and switch showed it in 4 wheel or 4 wheel low. I had a similar thing happen on a chevy and it was an actuator. I am thiniking it is something similar here. Any advice on chasing this down?