What is wrong with my indesit WD12?

It sounds as though the drum bearings have failed, this is usually because the bearing seal has failed allowing water to enter the bearing, which then very quickly wears causing the noise and movement you describe. The solution is to replace the seal and bearings. This diagnosis can be confirmed by asking a washing machine repair specialist for your make of machine, to check the machine and give you a quotation, this service is usally free,(do not pay for quotation) check before you get them to visit. Usually you require special tools to remove the bearings so unless you are a competant DIYer I would get a few quotes and pay some one to do the job. If it is left to long it will destroy the drum and you will need a new machine!

some one who has had the same problem
November 2005