what is the difference between limited slip and posi, which is better, if i were to change the differencial, would i need a new axel?

------------------
Trent
---Car---
89 Firebird/305 L03 TBI A4/t-tops
Open Element Edelbrock Aircleaner w/ K&N air filter/Summit Chrome Valve Covers
Edelbrock TES headers 3" out/flowmaster American thunder 3" exaust/Catco cat
---Stero---
Pioneer DEH-P730 Premium
Infinity 2way 4652 4x6's/Pioneer 4way ts-a6985 6x9's
profile cl640 110x4

the only differance between posi and limit slip is the spelling, it's the same thing. gm made 26 spline axles untill 90 then went to 28 spline

------------------
ICON Motorsports
1st & 3rd
MM Black Diamond 538 F&AM

As long as we're (kinda) on the topic, has anyone else noticed that there's a difference in the outer flange between the 26 and 28-spline shafts? I just put my newly-assembled axle in the car, TRIED to put the old rotors back on, and the ID of the rotor wouldn't clear the OD of the axle flange!

Btw, its an '84 disk housing that I put an SLP take-off posi and 28-spline shafts into.