Unknown noise

At low speeds with my driver side window down my truck seems to make the sound of dragging a chain or something metallic but only at low speeds. Any idea if this would be wheel bearings or the brakes dragging? I have crawled under and I haven't seen anything hanging down. The truck is a 1998 GMC Sierra.
Any help would be appreciated.

Have someone stand outside the truck and listen as you drive by, no way to tell what a noise like that is in this environment.

If you can tell which wheel the noise is coming from, jack that wheel off the ground and turn it by hand and listen for the noise.

//2000CAYukon

Thanks for the info. I appreciate it.