Any one of these parts can wear out and cause squeaking. The drive belt is the most common culprit because it starts slipping when it stretches with age. If the drive belt is loose, the drum probably doesn't turn smoothly when it is full of clothes. To replace any of these worn parts...
"Well, as this train pulled up to the platform I noticed that the wheels on the third freight wagon were making a squeaking noise. So in the interest of efficiency I felt it my duty to point it out to you." "Yes, well it's the squeaky wheels that always gets greased isn't it ...