I've searched all over and can't find anything like this... I just bought an 03 wrx wagon last week. Its in pretty awesome shape (all stock) but since a few days ago it makes noise while rolling backwards in reverse but with the clutch in. I don't notice it when backing with the clutch out or at any time in any other gear other than reverse rolling back with the clutch in. The sound itself sounds kinda like something is rubbing. Its rhythmic and directly related to how fast the car is rolling. Sounds like something that is turning rubs at a certain point each revolution. It seems to come from the transmission or clutch. (Maybe not,) but if I pull it out of reverse while its still rolling the noise stops. This is my third manual Subaru and I've never had this before. The car's only known issues at this point are bad sway bar bushings, worn front strut mounts, and the fact that like an idiot I've been putting 85 octane in it. (It didn't come with the owners manual and I only just barely saw the sticker inside the gas door). I'll try to get a look underneath tomorrow and check the drive shaft and any other moving parts for signs of rubbing, but any other ideas would be much appreciated.