Whirlpool Dryer Knocking Noise

7-year old dryer started making an intermittent, raspy sound last week. Taking it apart, nothing looked suspect. There was some minor rubber on the drum from the rollers, but, overall, the rollers still had some life in them. I swapped both rollers and the belt out. The idler pulley looked great, which was a blessing as the new one I got was bent; so, that stayed in.

After, putting it back together (and a good cleaning), the raspy sound is gone, but we are now left with a rhythmic knocking noise. We have wool dryer balls and I literally sounds like two of them are just tumbling around in there. Any ideas? Maybe I didn’t quite align the drum on the rollers? Everything looked good when I put it together. Drum seems to rotate smoothly when i move it by hand.

Hello and thank you for your question.
In order to provide most accurate advise we need the complete model number of the dryer.