I have a two year old Hope XC rear hub that’s started making some nasty sounding noises. Not sure what’s broken. It’s fine on the bigger gears but when I drop it down onto the smallest three cogs, it makes a nasty rattling noise, when I go over anything a little bit bumpy. It’s not just under load either, it also happens when I freewheel. The cassette is still fixed on tight, so it’s not that. Any suggestions as to what the problem might be?

After 2 yrs it’s due a service anyway, noises could be worn bearings,a broken axle or damaged pawls,assuming that it is the hub and not something else like the mech.

It’s not the mech. It’s definitely hub related.

strip it down and evaluate the situation there may be visable damage if not then try the bearings and re-grease the hub etc.

Try gripping both ends of the axle and turning then in opposite directions, if they move then it’s broken. Grip the freehub/cassette and try to wobble it, if it moves it may be the bearings.If you turn the axle and it’s rough it’s probably bearings, and if the freehub won’t freewheel when you hold the axle it’ll be the bearings too.