very noisy white knight cl767 tumble dryer?

i have a cl767 condensor tumble dryer which is making a very loud vibrating noise when its working. It does not sound like bearings rumbling, it sounds and feels as if its a much higher revving sound. it still seems to be working o.k. apart from that
has anyone got any ideas as to what it could be causing the noise and how to fix it?
thanks !

i.reidie@ntlworld.com
October 2005