Noise when running

If it was the belt, it seems it should slip more when loaded since the torque needed is greater then. A bad bearing might do just the opposite; holler when empty and quiet somewhat when loaded.
If the back panel can be removed without disabling the machine, it might be possible to locate the source of the noise better and it may not even be necessary to have the dryer running if (after unplugging it) the drum could be turned by hand while another listens at the rear.

It is probably the rollers that the drum sits on. When these get old they loose their grease and start to seize up. They will start to make a terrible noise when this happens. They are cheap but kind of a pain to change out. They sit on the front of the drum and some models have them on the rear. In order to change them out you need to remove the drum. Let me know if you have any other questions and let me know if this was helpful to you. Good luck and I am glad that I could help.