I just thought I'd post this and see if anyone has had a similar problem and might know what this is.

My truck has had this since I got it but it just keeps getting louder. When I drive my truck there is a loud metallic rattle coming from underneath the truck, it starts at about 2,000 rpm then goes away and comes back with higher rpms. It doesn't affect the driveability any it's just really annoying. Anyone else have this problem? Also, some days it doesn't happen at all, really strange...