A differential's main job, apart from transferring the propshaft drive to the wheels, is to regulate the amount of torque each wheel receives. On a bend, the inside wheel receives less torque and the outside wheel gets more to help steer the vehicle round. If this didn't happen, steering would become much more difficult.
However, this goes completely out of the window if one wheel starts to lose traction in an off-road situation. In this instance, a diff lock locks both halfshafts at the differential to that both wheels turn at the same speed. So if one wheel loses grip, for example, in thick mud, the wheel that has grip will continue to turn and drive the vehicle forward. Without a difflock, you would be stuck, as the differential would cut the torque to both wheels on the axle.
Limited slip differentials, meanwhile, use friction clutches to allow torque to be sent to the slipping wheel. This enables different wheel speeds and improves both traction and stability.
However, this goes completely out of the window if one wheel starts to lose traction in an off-road situation. In this instance, a diff lock locks both halfshafts at the differential to that both wheels turn at the same speed. So if one wheel loses grip, for example, in thick mud, the wheel that has grip will continue to turn and drive the vehicle forward. Without a difflock, you would be stuck, as the differential would cut the torque to both wheels on the axle.
Limited slip differentials, meanwhile, use friction clutches to allow torque to be sent to the slipping wheel. This enables different wheel speeds and improves both traction and stability.