Not necessarily. Auto hubs lock in each direction but when you change direction of movement, the hub unlocks momentarily and then re-locks in the other direction. Theoretically at least. This really sucks if you ever have to rock the truck back and forth to get unstuck (deep snow perhaps). The hubs are constantly locking and unlocking and become effectively useless rendering you more stuck than when you started.

 

Gotcha, but they still work in reverse, just might not be perfect...