What did I break?

I've got a '68 Barracuda w/ 408SB, Auto, 8.75 rear with 3.91 & Detroit Locker. Last week at the track when I left the light I heard a loud bang and the car lost traction at around 60' and again when it hit 3rd gear. We limped through the lights and limped it home (about 8 mi) with it intermittently banging away in the rear. It also now only has left wheel drive. From what I hear, the Detroit Locker is virtually impossible to break so did I break an axle? I have yet to have the time to tear into it, afraid of what I'm going to find.