Vibration after spring change

I didn't find any shims when replacing the old springs. This is a Minnesota car so the shims could have been some of the rust that came off with the springs. I've had air shocks on the car years ago and could raise/lower the car all I wanted with out any vibrations. I've got the car up in the air now and it still vibrates I just can't hold the speed for vibration and look under it at the same time. I'll have my dad over later to help me and I'll let you know. Also, is it possible to break something in the rear end by pounding it free from the springs?