buster

I heard an ungodly sounding almost creak coming from the rear end on the drag strip off the line. It was so loud and unusual that I thought I broke something and pulled over. Stock car, no drag radials and the car drives fine. Anybody have any opinions of what it was? I have probably made about 300 passes on a drag strip, but this car is new to me. Should I be concerned? Or are these noises normal?