I don't think its the CV's as all 4 tires slip and grip like they are locked in 4-Low. I starting to think its one of two things. T-case has been abused and never maintained or speed sensors are bad and sending false info.
On a secondary note, my "Winter" switch doesn't work. "Power" does. Could it be that the trans is starting in third all the time and because the switch is broken I can't turn it off?