So are you saying the TC does shift from 4H to 2H? By shift do you mean actually engage gears, because I believe the front shaft is engage in 2H the same as it is in 4H?
Or is there some sort of shift in the transfer case refering to a position that signals the vacuum to no longer be applied to the front axle actuator, when in the 4W positions (4H and 4LO)