[draker]

For manually operated lockers the axle shafts have to be moving at the same speed or with very little difference in speed to be engaged.

>Only engage the Eaton ELocker™ differential while the vehicle is stationary or operating at speeds of 3 mph or less with minimal wheel slippage.

This specific locker (Eaton G80) is self-engaging up to a set speed which is intended to prevent this from happening, though it has been known to occur.

>The G80 can be very effective when used within its limitations. However its very design can lead it to failure. It requires a certain amount of speed difference between both rear wheels to operate. Basically more slip than you would ever encounter going around a turn, but it will not lock at speeds above roughly 20-30mph. This it where it earned the name "gov-lock". It has a speed governor that operates off centrifugal force inside to govern locking.

When it locks, it locks hard. Imagine one tire sitting still, and suddenly being launched to a speed of 20-25mph. That takes a great deal of force and puts a lot of strain on internals. They have a tendency to break with no warning.

Page also has photos of one that has failed.

http://www.ar15.com/forums/t_1_134/1250761_g80_differential_...