When diving over about 32 MPH I heard an intermittent dinging sound, like light metal hitting against something solid. I couldn't imagine anything inside the engine or transmission that would make such a sound. It seemed to be coming from under the floorboards. So today I went exploring. I found a couple of the fan blades were shiny metal on the end, not painted. I gave the adjusting bolt a turn to raise the fan a hair. With the fan no longer hitting the crank ratchet, the ding is gone. Sometimes things are hard, and sometimes they're easy.
Steve, Congratulations on your find and thanks for sharing.