Differential Locker
A mechanism that locks the differential gears together, forcing both wheels on an axle to turn at the same speed regardless of traction.
A differential locker (or locking differential) is a traction-enhancing device that locks the left and right axle shafts together. In a standard open differential, power is sent to the path of least resistance; if one tire loses traction on ice or mud, it spins helplessly while the tire with grip receives no power.
A locker forces both wheels to rotate at the exactly same speed, ensuring that even if one wheel is lifted completely off the ground, the opposite wheel will receive full torque to move the vehicle. Lockers can be automatic (engaging when wheel slip is detected) or manual (activated by the driver via a dashboard switch using air, cable, or electrical solenoid).
Using a locker on dry pavement can cause severe tire scrubbing, binding in the drivetrain, and hard steering because it prevents the wheels from turning at different speeds around corners. Lockers are primarily used for off-road driving, heavy towing, and severe winter conditions.