Rear hubs - serviceable?

I've got a bit of noise from the rear end of my bike going over bumps, and I'm fairly sure it's the rear hub. It's got quite a lot of slack in it, and quite a 'metallic' sound when the free hub bites when you pedal.

Assuming my diagnosis is correct, what are my options? The hub is an XT - about 3 / 4 years old I guess. Are the 'innards' replaceable, or do I just by a new one and get the wheel rebuilt with the new one?

Thanks,
Mike P


http://www.flickr.com/photo_zoom.gne?id ... 519&size=l