[Alan Roehrich]

That's a place to start, at least in my opinion, for whatever that's worth.

Have you taken your springs and shocks off, and used a floor jack to move the rearend through it's travel to the limits to make sure there is no binding, and to see how the pinion angle changes? You should make sure you check it all carefully, especially at the point where the car launches. The rear suspension should separate in order to plant the tires, and you need to check the pinion angle with the rearend at the point of its travel that it is at when the car launches.

Have you checked all of the attachment points for the suspension, and all of the weld joints in the rear frame? You need to make sure there's no flexing or cracking going on back there, it is not at all uncommon to see things moving around back there when one of those cars is raced.