Hotpoint dryer drum really stiff!!!!!!?

Hi, my hotpoint tcm580 dryer drum is really stiff and will not start-just hums.
It has been squeaking for a while and now it's not working.
The belt is fine and when I take it off the jockey wheel the motor spins really fast so I replaced the jockey wheel to no avail!!! Please can someone advise me? Many thanks :)