What is the real differences between Posi, limited slip and locker? Also some People seem to think that posi is like a full locker rear-end and some people seem to think it is the same thing as a limited slip differential. I've checked around and cant find if posi and limited slip are the same thing or if posi and locker is. if posi and limited slip is the same thing how come people think that posi means that both wheels spin the same all the time like a locked rearend? This is confusing. what is the real meanings or differences from the automotive companies

 

GM uses posi and limited slip interchangeably. Posi has never meant that both wheels were constantly locked together in any auto community I have ever been around.

 

As Rob points out "posi" is a GM term for a limited slip differential. It dates back to the 1950's when GM trademarked the name "Positraction" for the limited slip differential available on the Chevrolet models (and maybe Buick?). Pontiac called it "Safe-T-Track". At that time, these were typically clutch style limited slip units. "Posi" is in no way similar to a "locker".

My first new car was a 63 Impala coupe. It left the factory with only three options - 300HP/327ci engine, AM radio and Positraction.

 

Thanks