[Roosell]

The verdict: Clutch assembly. The repair shop insists that the clutch in the car was the wrong clutch (possibly a disk and pressure plate from an S model?). The center of the clutch disk was larger than the transmission input shaft, and they were surprised the car ever moved. Fortunately the input shaft wasn’t damaged when the clutch plate finally lost its grip and started freewheeling. The pressure plate fasteners weren’t completely tightened / flush, and had struck something while rotating. They were bent, and had to be cut out.

The pressure plate diaphragm fingers didn’t match up with the throw out bearing properly. The bearing barely touched the fingers. The rub marks are visible at the very tips of the fingers, and it looks like eventually the throw out bearing would have been pushed inside the ring of fingers. For sure, the clutch peddle action is much lighter now! The flywheel was damaged, so I got to buy another one ($900!). This has been quite expensive. Thanks for the input, guys!