and it not my stereo.. I've noticed the past day or two when I pull into my spot at work I'm getting a nasty metal on metal buzz sound. sounds like a heatshield to me but I dunno. only does it in drive and reverse and only when idle at a stop. as soon as you give it gas it stops.

 

I think I may have the same sound from my truck. Only mine happens about 5 seconds after I start my truck, lasts about second and seems to be coming from the passenger side by the firewall. Definitely sound like a metal vibration.

 

Sometimes I get that buzzing, noise upon start up, however it only occurs in the winter when the mornings are extreemely cold! I think that it is a vibration....that is what it sounds like!

 

mine doesn't make the sound on startup. only after the truck is at operating temperature. I got under there after work and it sounds like its coming from either the drivers side heat shield, cat or transmission

 

Styx i hear...mine does the same thing only when i accelerate, god awful sound. Takin it to the shop within the next 2 weeks cant take it anymore...might be caused by the vaccum line by the hub? when it is in 4 wheel drive you can not hear the sound.

 

Loose intake tube connection at the fenderwell maybe? Mine did that once and it made a racket like that at the times you describe, Styx.

 

I have a similar noise. Only in gear with foot on brake. As soon at the truck moves it goes away.

 

yup thats it, its impossible for it to be the 4wd hubs, and its not coming from under the hood

 

I had this same vibration. Drove me crazy. It stopped when I added the AF1, the efans, and the u/d pulleys. Did them all at the same time so I don't know what was the cause. Air intake tube, as mentioned above, sounds like a likely candidate.