What is the difference between an open gear and positrac unit?

[RoscoePColtrain]

hey guys,

I'm trying to learn as much as I can about the inner workings of the Charger and was wondering what is the difference between an open gear and positrac unit?

[Harlow]

A sure grip (mopar talk for posi) "locks" the wheels so they will both spin the same. An open rear end will allow one wheel to spin while the other wheel just sits there. Thats the best I can do. Someone else will chime in with more info.

[Nacho-RT74]

http://auto.howstuffworks.com/differential.htm

for positrack/suregrip, look at limited slip/clutch section

[Big Lebowski]

  Hey...the words posi-trac are not allowed here. That's a Chevy term, we say sure-grip. Open gears leave one long burnout & the sure-grip burnout cooks both rear tires & makes the car harder to control, kinda like driving a dragster on ice.

[hemihead]

A Sure Grip does not allow both wheels to spin the same.