drum stops turning after a short time

The drum would stop turning after running about 15 minutes. Then it got to the point where it would not turn any more. By taping in the door switch, I could get it to run after giving it a helping start. Then it wouldn’t even run with the helping start. I noticed the idler wheel was not turning. The wheel was severely worn down. I removed the drum belt and the motor runs fine by itself. I replaced the idler assembly and the drum belt. I cleaned the lint off the motor, which wasn’t much. It still did not fix the problem. The drum stops turning after a few minutes and a buzz sound. What specific parts should I consider replacing next? Everything else is original except some heating parts. I would also appreciate any instructions on how to replace whatever other parts you suggest. Thank you.