differentials

[pilot]

I got a 69 right wheel wonder in Colorado.  I want to road race as well as drag.  What kind of diff do I want? A limited slip or a posi?

[JohnZ]

"Limiited Slip" and "Posi" are the same thing.

[william]

You will not want positraction on a tight road course-that's why the standard Z/28 axle was a 3.73:1 open. Can't have your cake and eat it too I guess.

There used to be an "air locker" diff that you could turn on/off but I do not know how well it worked. Do not hear much about it anymore.

[hotrod68]

  Pontiac made an 8.2"  positraction 10-bolt for the Firebirds that is a great compromise, if you can find one. Unlike the Chevy positive traction carrier, it didnt have conventional preloaded springs and clutches but it will power both wheels in a straight line. It also doesn't have C-clips--the axles are held in by bolts at the brake backing plates. It's a bolt-in except for having to use a bastard U-joint and brake hose.
  I tortured one of these things at the drag strip many times with a slicks in a mid-12-second car and it never broke, so it's strong, too. Just a thought. Good luck!

[69Z28-RS]

William? Are you of the opinion that Penske and other Trans Am teams did not run posi rears on their cars on the Trans Am  and IMSA-GT series???    That would be the opposite of my understanding if true.....  and they Were running road courses!   In fact, the Service Duty 4-sheel disk brake rears came with HD posi units with heavier springs, more plates and 4-5 times the breakaway load as the standard posi units!