Similar prob with Zanussi Aquacycle 1050.
Noisy drum on full spin & some black oil or lubricant leaked into drum last use.I think bearing seal is gone & now it's running dry, perhaps u have same?
Check the nuts tight holding the large belt wheel at back of drum.The movement fwd & bwd you've found is normal for any drum as it's freely suspended on springs within the machines casing to allow for vibration.If it were secured firmly to the machine's casing it would try jack-hammer your floor with the forces exerted on full spin!
George
February 2006