This is my first time on the forum and I have to ditto the last guy.Thanks for spending your time and putting some knowledge on us.Also,my car used to drift left,added a 1/4lb air to driver side tire and shot straight from there.Looking back now,I think it was a lucky fix to a rollout issue.Thanks again.

If negative preload was added, then the car would move more to the right then when you started. If adding preload did not break a chassis mount, odds are things are solid. Tire rollout would have to be pretty excessive to create the pull you are talking about. If I was a betting man, I would guess your entire rear end is out of square. This could be as simple as the rearend sitting in the car sideways right down to a bent rearend. I would encourage you to pull the rearend and check to make sure all is straight. While you have it out, inspect all your rearend brackets. Reinstall the rearend. If you have never squared a rear, make sure to have someone with you that knows what is going on. If you have a local chassis shop, get the car together and get it there to be scaled. Good luck to you.

What do you have as rear springs ?......if its pulling to the right...add a little rebound to the left rear spring ?

Brian