185,000 miles Inline 6. I wish I could, but it's hard to tell. It sounds like its coming somewhere from the center back, but I can't tell if it's coming from underneath. Someone said it could be a drive shaft problem or something related.
I did check the pulleys and belts and they all seem to be working fine. I thought it could be that since the noise occurs when the car is simply idling.
Thanks for the response!