The dryer made a random grinding/rubbing noise during operation.

After removing the lower access panel, I observed the drum and belt and saw it turning freely. The support rollers in the back turned freely and were in good condition as well. At odd intervals the unit made a humming or grinding noise, and i decided to check the blower wheel (the other rotating part in the system). I found that the central hub of the wheel (which is made of a nylon like plastic) had sheared off from the wheel itself. I ordered a new part and started to remove the old wheel. **NOTE** many of the stories I read described how this part would have a reverse thread, it did not and that cost me an extra 30 minutes to figure out (the new part had arrows showing the correct direction to put on and remove - the original didn't). Once everything was cleaned and reassembled, I started the dryer again, but got no heat. I had previously replaced the heating element, so I thought my wiring was wrong. That wasn't the problem, but a hint from this site about checking the incoming wiring was the solution, my ground wire had come off the terminal in the back of the dryer and I wasn't getting the volatge across the element that it required. With the ground wire back in place, everything worked fine.