My Ultima CTD80 makes a rumbling sound or rubbing sound. ?

My Ultim CTD80 Makes a funny rubbing sound, iv'e taken part of back off and there is a small plastic fan. iv'e cleaned this and when i turn drum one way then the other way the plastic fan makes this noise. i noticed that it takes longer to reverse from one direction to the other . can any one help as this noise is doing my head in every time my wife is drying clothes.