Locking differential

An open (or unlocked) differential always provides the same torque (rotational force) to each of the two wheels on that axle.

Others, sometimes referred to as lunchbox lockers, use the stock differential carrier and replace only the internal spider gears and shafts with interlocking plates.

Some other automatic lockers operate as an open differential until wheel slip is encountered and then they lock up.

These types generally use an internal governor to monitor vehicle speed and wheel slip.

Some other automatic lockers operate as an open differential until high torque is applied, at which point they lock up.

[4] Mini-spool uses the stock carrier and replaces only the internal components of the differential, similar in installation to the lunchbox locker.

A full spool is perhaps the strongest means of locking an axle, but has no ability to differentiate wheel speeds whatsoever, putting high stress on all affected driveline components.

Automatic locking differentials also affect the ability of a vehicle to steer, particularly if a locker is located in the front axle.

[5] Traction control systems are also used in many modern vehicles, either in addition to, or as a replacement of, locking differentials.

Sensors monitor wheel speeds, and if one is rotating more than a specified number of revolutions per minute (e.g. 100) than the other (i.e. slipping) the traction control system momentarily brakes it.

This transfers more power to the other wheel,[6] but still employs the open differential, which is the same as on cars without the EDL option.