you can make new "bearings" for your fan, if you want to renew old fans. its not that hard job to do, but you must know what you do. the noise is propably the bearings on your fans. i have have that in my 3dr. i will renew my fans, just for the fun of it.

but the fans are quite cheap, so maybe new fans would be smarter. changinf those fans, are easy job.