Every 4X4 I owned that had the shiftier for the transfer case on the floor all had issues with the linkage freezing. I would drive to the quarter car wash spray hot soapy water all over the linkage and it would work fine.
Now I plowed with my trucks and attributed that to the snow and slush getting packed around the linkage. If the transfer case it's self is sticking it time to change the fluid and go with trans fluid. All of my Ramchargers were changed over from gear lube to trans fluid as recommend by Chrysler. Check with a GM/Chevy dealer to find out what fluid they recommend.
Don