Weird noise 85 911

[csmab]

Happy New Year,

Ok - it seems as I get reacquainted with my 911 after not having one for 18 years I am always questioning myself if certain sounds are normal. This site as always helped me. My last noise was a ambient air valve which the forum diagnosed within a couple of hours. Still have the noise in the cold but isn't a big issue. Today after a 40 minute drive I had the most unusual sound coming from under the car. It was a scratching noise under the car between the front and rear seats. Sounded like a cat trying to claw it's way into the interior from underneath. It is only when driving. At idle no sound when stopped. The sound is not constantly present either. Very strange. Engine sounds fine. I looked under the car at everything looks normal. I am now afraid to continue to drive to diagnose the sound for fear that I might be making it worse by creating more damage. Any clues???

As always thanks,
Craig