I recently purchaed an '03 s60 2.5 AWD T. It has 44,000 miles and operates great. The other day we had approx. 1-2 inches of snow and the roads were covered with snow and slush. The first time I have opearted this car in those conditions. After about 2 miles there was a very high-pitched soundlike metal on metalcoming from the rear. It would subside in lower speeds, but regain pitch at about 30 mph. Now that the roads are clear, the sound has disappeared. Thoughts?

 

Did any of the tires seen to be slipping at all?
I wonder if it was something from the TRAC's system.