Ok looking at a mates bike for him as it keeps on slipping when changing gear. Have just taken the hub apart as though it might have been the freehub body but that feels ok no adverse rattles or looseness. I struggled to get the cassette off with a chain whip as the chain whip kept slipping off. So I think it is the cassette that is knackered but what are the signs of a knackered free hub?

Cheers!