posi vs limited slip. what the difference if any, and what is better for off roading?

 

Posi
(positive traction) is a GM term, and LS is a Ford term for exactly the same thing.
Clutch type differential used to apply resisatnce to the side gears in an attempt to distribute power (bias) to both axle shafts.

 

Positraction (GM) EquaLock (Ford) Sure-Grip (Chrysler) Borg Warner Spin Resistant (for Chrysler, called Sure-Grip) Dana Power-lok (for Chrysler, also called Sure-Grip) Twin-Grip (AMC in the old days)

There are others, most of these are the clutch type limited slip. One is cones, but they all are "limited slip" diffs relying on spring pressure and friction to keep the axles turning together under power, but allow differential action in turns.

Lockers use more mechanical locking methods like ratchets to lock the axles together, they are noisier and more harsh.

"Posi" became the term applied to all because:

--GM was the biggest and pushed it and there were more positractions out there.

--It's easy to say

--It is an almost perfect term as it is what it says--positive traction.

--It's a four-letter word.