Beginning in September of 2005 I posted messages regarding a very annoying noise in my XLR which occurred mostly at 20 to 40 mph under slight power. A couple of owners reported similar noises but no one had a solution. This week my friend the service manager at Ed Morse Cadillac in Delray Beach Florida went with me for another ride becsue I was seriously considering getting rid of the car. He discovered that the noise occured at 1400 RPM's regardless of vehicle speed and also disappeared if we turned the air conditioning off. This was the clue to solving the problem. There was a vibration in the a/c high pressure line and also in the low side suction line next to the cowl. This vibration was being transmitted throughout the car and was easily corrected by adjusting or bending both lines. 15 months and 6000 miles later my XLR sounds like the powerful V/8 it is and I am very pleased and anxious to share this info with others who must be experiencing the same grinding sound that really sounded like transmission noise. Hope this helps someone else.