Hi and welcome to the Gigabyte Forum.
From your description of the problem I have no hesitation in recommending that you RMA the card as the fan is obviously faulty. These cards are noisy just because of the amount of air they push to keep them cool but it shouldn't be rattly just loud.
Hi Just wanted to let anybody who was considering buying the following:
I got a replacement card with no problems and the card is really excellent when it is working correctly, however;
I actually had 2 of these in SLI for a bit, which my friend now owns.
There is definitely an obvious fault with these cards where the cards get noisy when they are too hot. My friend has the exact same issue in his setup
and one of the fans starts to make a rattling noise which can be aleviated by putting slight pressure on the fan shroud.
My advice if overclocking these cards, don't let them get anywhere near the Nvidia rated thermal threshold spec for gf100 (105 degrees) or you will run into noise issues.
This could also cause problems for some of you in sli as the cards dump the heat inside the case so the top card can end up a fair few degrees hotter than the bottom.
I could not live with the heat issues in my setup and am currently running a single 580 which exhausts the heat straight out of the case.