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How have you tried to shift it out of four low?
How did you try to shift out of four low?
To shift out of four low start by driving in a straight line at 2-3 MPH. While still rolling put the transmission into neutral. Then switch the transfer case switch to four high or two wheel drive. As the truck coasts to a stop the shift will complete. Then you can put the transmission back in gear and drive off.
If that doesn't work then there is something wrong in the system. It could be the transfer case motor, front axle disconnect actuator, TIPM, or wiring between any of the components. A scan tool will be needed to see what fault codes are stored and start diagnosis.