I'm going to be changing out the rear end within the next few months and am trying to find out what would be the best choice for my car. Its going to be used for auto-x and road racing on the weekends and to get to work every day. Theres going to be a 500-600 hp LS1 pushing it when the projects done. There seems to be quite abit of info here about the 12-bolts and 9-inch rears but nothing for the quick change.. From what I've read it sounds like the 12-bolt is a better choice for road racing (less drag), but I'd kinda like to have the option to change out the gears easy if I wanted to.

 

You can install any diff you want if you have enough time or money. Chances are you're not going to be swapping gears frequently enough to require a quick change diff. This is mostlty used now on oval dirt track racing. Your best bet is using a 9" diff. To change the gears you'll need a second center section, carrier (posi) and gears.

Drop the driveshaft, pull the axles, drain the oil, pull the center section out. Install new center section, reinstall axles and driveshaft. Refill with oil. All this could be done in about 30 minutes.

The differences between a 12 bolt and a 9" are so little, you're not going to notice any difference if you tried both. Both have advantages and disadvantages. It just becomes a personal preference. In a racing class, you might not be able to mix manufacturers parts. This means you wouldn't be allowed to use a Ford diff in a GM so you would have to use a 12 bolt. I don't know if this rule is in any autocross classes.

Always read the rulebooks before doing any changes just to see if they're allowed or not.

 

So what are there the real differences between the 9-inch and 12-bolt? Any brands to stick with or shy away from?