I have a better solution.  What I did with a 4770 and a 6870 when the fans died, is I took off the plastic shroud (you have to take the whole cooler off) and then reattach the heatsink without the fan, so it's just a big heatsink.  Then you can zip-tie an 80mm or 92mm fan to it, and you'll find the card runs at like 50 degrees now, total upgrade!  And it doesn't cost anything!