Yeah, basically you can drive with the spool, but it's mainly for going in straight lines. A lot of people don't like them because it's essentially like someone welded the diff gears in a demo derby car or something like that, it's easier to drift the vehicle dirt track style than to drive on pavement around corners.
My friend's Mustang would chirp the tires like crazy if he turned. He just removed it and is putting something else in because he wants to take the car to shows and stuff also in the summer. He didn't even register it this year he said it was so bad.
My SS has some kind of a weird rearend in it that I haven't figured out yet. I'm starting to think it's a Detroit Locker or an Eaton locking diff like what comes in the GM trucks. I've come to the conclusion that the only way I'll know what's in there is if I pull the cover off because I get so many different opinions from people regarding which direction the tires spin when you jack it up, if you can spin one tire by hand with the other still on the ground, etc.