what is the difference between a posi and a locker?

I have been looking through magazine at different posi units and i have been wondering what is the difference between a posi and a locker. also is there any difference between a posi and a truetrac system?

 

I have the tru-trak system. I wanted a system with no clutches to wear out. For me, the locker is louder on the street but with 40 series flowmasters and a grumpy cam, who can hear it. I am hapy with it so far.

 

Limited slip tends to send a portion of power to the non-spinning wheel by friction of some sort. Usually clutches. The spinning tire absorbs the lion's share of power output.
A locker will tie both wheels together through a solid mechanical link, so both wheels share full power. When it is locked, you have a spool, when you turn corners, you have a differential.
Dave

 

I hope I get this right...

All those you mentioned are a form of a limited slip differential. Posi-traction was what General Motors called their limited slip. Ford called theirs Traction Loc. Locker is short for Detroit Locker, a maker of limited slip differentials. TrueTrac and PowerTrax are the brand names for Richmond Gears limited slip differentials. Auburn is another available. All these "lock up" the differential and make it act as one straight axle, under acceleration, once a certain RPM is reached in the diffential. The difference between these is how they accomplich this. some use fiber clutches, some use gears and pins, and some use a combination.

If I left out a detail or got some of the facts muddled, you will be given the correct answer.

 

No matter what you call it, any type of locking rear is supposed to send power to both rear wheels equally. The way they do it is the difference. Either by clutches, cones or mechanical links. The clutches are quieter and slip much easier for going around corners where as the mechanical type are more noisey and will not slip as much. The cone type are kinda in the middle.

 

In theory, but they don't.
The clutches in a limited slip are only activated by the excessive spin of the primary drive wheel. The power distribution is around 80/20, maybe 70/30 on asphalt. Granted, it is good enough by far to warrant use of clutches and help traction along, but it is far from 50/50.
I broke one side of a locker once... behind a Powerstroke diesel of all things.
I called the manufacturer and complained about constant burnouts with one tire just by touching the throttle. I would pull away from a green light with the tire roasting on a 1-ton van, without trying.
That is when he told me what broke... but the interesting part is that he said a broken locker sends 100% of torque to the functioning wheel, that is why I couldn't get traction. I thought it would have been like a worn posi or open rear, but he said no. The funtioning axle on the locker was now 'hard wired' straight to the driveshaft with no way to disengage at all. Clutches and open diffs suck up power to 'nowhere', no matter if they are spinning one or two wheels.
If it wasn't so annoying to break an expensive locker, it would have been fun.
500 ft/lb torque to one tire is a frickin blast.
Dave