I recently started to hear a metal grinding noise from what I thought was one of the front wheels on my 2008 z71 Tahoe. I first heard the noise while turning at slow speeds so I thought it might be something with the front wheel, but every once in a while I will hear the same noise while idling. I can't seem to pin-point the source because I have not been able to get the noise to duplicate while I'm looking in the engine bay. I did change the serpentine and a/c belt a few months ago, and had the brakes changed, the front driver side needed a whole new caliper. I don't think they are related to the noise, but I don't know what to look for. No change to driving characteristics, but the sound is driving me nuts!