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I'm also confused about the difference between "lockers" and "traction lock". What IS the difference?
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To start with, a differential transfers torque from the driveshaft to each axle/wheel. The common 'open' differential refers to the gears being able to transfer torque equally to each wheel, so if one wheel spins, the other wheel is virtually helpless as far as traction goes.
The "traction lock" unit applies torque through a set of conventional clutches - steel plates and friction discs preloaded with a spring. The unit applies torque evenly to both wheels, but in turns or where one wheel's traction is extremely different from the other wheel, the clutches slip enough to equalize the traction or allow one wheel to travel farther as the outside wheel in a turn.
http://static.howstuffworks.com/gif/differential-limited-slip.jpg
"Lockers" apply to differentials that 'lock in' with a mechanism controlled by the driver. When 'unlocked' one wheel is free to spin independant from the other - as in the common open differential. When 'locked', each wheel rotates the same as the other as power is transferred to both wheels irregardless of traction. Electrical solenoids or pneumatic control are common locking mechanisms.
http://static.howstuffworks.com/gif/differential-locking.jpg
Extreme abuse in a traction lock unit will burn out the clutches and render it ineffective. Extreme abuse in a locker will probably result in broken parts.
For further info:
http://auto.howstuffworks.com/differential.htm