A differential, when one is talking about vehicles, is a mechanical piece of the car, truck, or SUV which allows the powered-wheels to turn at different speeds. This would be the front wheels in front-wheel-drive, the rear in rear-wheel drive, and all wheels on all-wheel drive. This is necessary because when taking turns the wheels need to go different distances, and if they both always moved at the same speed you would end up damaging your tires and possibly other mechanical parts.
Read More: All-Wheel Drive vs Four-Wheel Drive
Why Is a Locking Differential A Good Thing
While in general driving you want your wheels to be able to spin independently for comfortable turning, this can result in a loss of traction in some circumstances. If one wheel slips on ice, the differential may continue sending power to that wheel, causing it to spin, while the wheel that has not slipped may have less power.
Also if one wheel gets stuck, but the other is free (like what might happen when off-roading in mud or over rocks) then the differential might continue sending power to that wheel, making it spin wildly, while not really helping you get out of the mud.
With a locking differential (whether automatic, or activated by the driver), the powered wheels can be united. This allows drivers to have better traction, and can be extremely helpful either for getting out of mud and snow, climbing rocks on the trail, or maintaining traction in a snow storm.
While a driver shouldn’t keep their differential locked in highway driving, it can be very useful when off-roading, or in some high-performance driving situations. Some vehicles that feature locking differentials include off-road models of the GMC Sierra and Chevy Silverado, and the 2017 Chevy Camaro ZL1.