I didn't either before I came here. I knew about how they worked and that's about it.
Basically a limited slip, (ie, Posi, Trac-Lock, or the clutchless Torsen) all work on the same principle. There is a torque biasing between each wheel. To make things simple, say the torque bias is 2. So that means one wheel can supply 2 times the torque (grip) of the other. So if one wheel is on a less firm (traction) surface the other wheel can supply up to 2 times the amount of torque to the other wheel before it begins to spin.
Simple examples.
1) Both wheels on same surface.
Duh, they will both grip equally and spin together, no need for any torque biasing.
2) One wheel on solid ground, one wheel on soft or slick ground.
This where it gets tricky. Suppose the slick tire is able to provide 100 ft lbs of torque before it spins, then the other tire is able to provide 200 ft lbs of torque before any slippage in the diff occurs, giving a total of 300 ft lbs available to move the vehicle. OK. So then, if 300 ft lbs is enough to move the truck then everthing is good.
But if your in a ditch, deep mud or trying to climb, than the 300 ft lbs may not be enough to move the vehicle. OK, So what happens. Basically as you provide more torque with the throttle, the slick wheel increases to its maximam traction torque provide by the surface, the other wheel biases to its maximum of twice the slick wheel and then the L/S breaks free allowing the slick wheel to spin like an open diff. This demonstrates how a limited slip is beneficial, but is limited in its capability.
3) One wheel on the ground, one in the air or barely touching
So your suspension is flexed to the max and one wheel is surrounded by air, or barely touching. Well, air doesn;t provide much traction, I would say approx 0. So, the other wheel provides twice that, = 0. And now you have one wheel spinning in the air, just like an open diff.
Lockers.
Three basic types. Full, Selectable, Auto.
1) Full
Also known as a spool, locks both wheels together all the time, like a solid axle on a go-kart. Not recommende for street use.
2) Selectable
Allows driver to switch between full lock and open diff. Most common is ARB.
3) Auto
Provides full lock capability while automatically disengaging. It's kinda hard to explain. It is usually fully locked, but automatically disengages when different tire sppeds are encountered while cornering, however it will lock up if additional torque is supplied to accelerate through corner. Most common is PowerTrax.
Most of this information can be found searching for PowerTrax, and Torsen.
