So my vibrate doesnt work, I can hear something spinning inside, but cant feel the vibrate. When I shake my phone I can hear and feel something rattling around inside. Almost sounds like a screw that has come loose or the vibrating mechanism and its just freely roaming around the inside of my phone....

I want to take it apart, but fear I will screw this up worse. Is this something that is covered under warranty? and will they still fix a hardware issue even thought I have an unlocked phone?

This is definitely cover under the warranty but I heard that Apple may refuse to service iPhone without active AT&T contract.

...im in MExico city. i fix this problem open the iphone and assamble the small semicircular part, this part is the part that´s make the iphone vibrate, i have this problem after my little brother cross with his bike over my iphone . :-) ...you can go to ifixit.com for how open the iphone!