If you jack up one wheel and the other is still on the ground, it won't turn unless the transmission or tranfer case is in neutral. Now, if the transfer or trans is in neutral and the whell still won't turn in either direction, them it might have welded spiders or a spool ( none of which came from the military). Even if it had a Detroit Locker installed and was in neutral, it will still spin in one direction but you will hear a ratcheting sound. If it has a real tight friction type posi like the Powrlock, it might require some effort to turn but can be turned. Spring for a gasket and a few qts of gear oil and have a looksee. Now as far as high loc and low lock, those are transfer case functions. The NP 203 case has a differential within that allows the front and rear axles to travel at different speeds. Just like an ope rear end once a front or rear loses traction or is jacked up, you can't move. The loc function locks both front and rear axles together to elimiate this. Just remember this posotion is to be used for off road and slippery surfaces only. Use on hard ground gives adverse handling and possible parts breakage.