Added an update to the original post, below:
I put the car on jack stands for a more sensitive clutch drag test:
- With the parking brake on and clutch in, the gear was hard to gate (as before). I also noticed that the engine speed was responding and dropping slightly despite the clutch being in
- With the parking brake off and clutch in, the gear engaged smoothly. At first the wheels only spun a few revolutions, but quickly came to a stop.
- However, I also began to notice intermittently that the wheel would continue spinning while in gear with the clutch in at idle engine speed. This did not occur on every engagement, but occurred often enough not to be a coincidence.
- Also, wheel spin would occur at the same rate/sensitivity regardless of how far past the friction point the clutch was pushed in. In other words, the drag appeared to be consistent across the dead pedal throw depth.
- Nuance with this dragging incidence: when racing the engine, wheel speed did not increase appreciably or would decrease momentarily until RPMs returned to idle. This might explain why primary clutch drag tests turned out negative.
Based on these conclusions, I might be observing some drag due to the throw out bearing?
I don't have any grinding or shifting issues while the car is in motion or when the wheels are free to spin. Again, only happens when the car is hot.