Spent all weekend tinkering. Did the Seafoam oil change, and the clack has diminished to a ticking flutter that comes and goes. The noise almost always disappears right when the tranny shifts around 35 MPH. Any idea why that would happen? Should I change the oil with Seafoam every few hundred miles for a while to see if I can calm the flutter?

After several hours of messing with the belt tension, I seem to have the squeaking noises under control. The engine sounded pretty good with the belt off. She idled a bit rough, like she might be missing once in a while. Going to replace plugs and wires when I get paid Friday. Low budget is teaching me a lot about wrenching.

 

The clatter turned out to be loose bolts on the flexplate that bolts to the torque converter. They were hitting the plate on the front of the bell housing. Tightened them up, that noise is gone. Of course, there are a million other little noises I notice now, but that one was overbearing.

It's such a huge relief to know that clacking wasn't coming from inside the engine!!