What's the 'DIFF'?

[Longhorn Man]

I know what spool, locker, and a posi, all mean...and how they act....but what exactly is a limited slip, and an open diff?
Are they the same?
This is one area I know practicly nothing about.

[mikep]

Positraction is the GM brand name for a limited slip differential. A limited slip differential uses clutches inside the differential to allow one wheel to turn at a different speed than the other when going around corners so the axles dont bind. An open differential uses spider gears to allow one wheel to turn at a different rate but does not "lock" the axles together when going straight. clutch type positractions never do lock the axles in reality . The slip a little even when the vehicle is going straight and traction is lost but the slip is limited...get it?

Lockers mechanically lock the axles together with a gear mesh setup that unlocks when side force is applied. They do not "slip " when going straight . They "ratchet" to allow the tires to turn at different speeds in a corner. They can be a little unnerving when negotiating corners with the tires spinning as has been known to happen.

['72 Shorty]

To add to that, A spool is basically a solid hunk of metal that the ring gear bolts to and the shafts go in. There is no allowance for different tire speeds, and they tend to be really squirrely on the street and wear rear tires fast. A locker locks the 2 shafts together when going in a straight line, but allows one side to turn at a different speed when going around a corner. they aren't nearly as strong as a spool, but alot more street friendly. Just don't hammer the gas around a corner with a locker, or you will think the rear end just exploded.

Dangit Mike, you edited before I could finish.