True Locking Differential vs. Air Lockers

Your vehicles differential changes the rotating motion of the driveshaft to rotation of the axles through a ring and pinion drive gear, side gears and pinion gears. Differentials fall into three main groups: open, limited-slip and locking. There are several types of locking differentials. The original locking differential was automatic, other locking differentials have been developed that are manually engaged by air, electricity and cable.

Open Differential

Most vehicles are equipped with open differentials. When your vehicle makes a turn, the wheel at the outside of the turn has to turn faster than the inside wheel. The open differential allows this. Unfortunately, in low-traction situations, such as dirt, mud, snow, or if one wheel is in the air, all of the power is sent to the wheel with the least resistance, or traction. That wheel will spin and the other will do little or nothing.

Limited-slip Differential

Popular in high-performance vehicles, limited-slip differentials use friction discs or other methods to transfer power from the low-traction wheel to the high-traction wheel. The advantage of a limited-slip differential is that it allows the wheels to move at different speeds under normal cornering conditions. They do not, under most conditions, positively lock the axles together.

Locking Differential

Locking differentials use gears to lock the two axles together when power is applied to the differential, and work automatically. The wheels will both turn at the same speed regardless of differences in traction. Locking differentials make a clunking sound as they engage and disengage and can cause some unusual handling characteristics on the street. Too much throttle when cornering can cause the differential to lock up and try to push the rear end toward the outside of the turn. Locking differentials are popular in off-road applications and are mainly used in rear axles but can be used in front axles with locking hubs.

Air-Locker

The air locker offers the best of both worlds. When disengaged, the differential operates like an open differential, providing smooth road manners; the wheels are free to operate at different speeds. When engaged, the two axles are fully locked and rotate at the same speed even if one wheel is in the air. The axles stay locked until disengaged. The air locker is controlled with a switch that operates an air pump. A diaphragm is mounted in the differential that locks and unlocks the axles. Air lockers are effective in front and rear axles and because they are manually engaged, front locking

Other Lockers

In addition to air-lockers, there are electric and even manual lever and cable controlled lockers. They provide the same benefits as air-lockers but implement it differently.