Locking differential

A differential with the ability for locking together the two half shafts, thus putting the differential out of action and greatly improving traction. In a non-locking differential if one wheel was stuck in snow and spinning, the other wheel would be stationary even if it were on dry ground. In a locked differential, both wheels would turn the same amount. Since the dry-ground wheel had traction, it would be able to pull the vehicle out even though the other wheel had no traction.