Peter's brother-in-law Richard here.

I did most of the job at my place, so Peter isn't to blame if I screwed something up.

The pilot bearing is new, and I made sure it was seated fully, without beating it to death. The throwout bearing is also new.

The flywheel was resurfaced by a reputable pro-grade auto parts store, on a dedicated grinding machine. They said they took their time because it "had a few hot spots". There were some small, short radial cracks visible on the surface of the flywheel before the job but they said it would clean up OK. There were no visible flaws after the surface was ground. They ground the surface that mates to the pressure plate to maintain the relative depth between the two surfaces

I made note of the instructions in the Bentley manual that said to make sure the orientation of the clutch disk was correct, so I'm pretty sure I got it right. It wouldn't go together all the way if it was backward anyway, would it? If it did go in backwards, so that the cushion springs weren't able to work, I can see it acting like this.

I was finally able to reliably reproduce the problem myself today. I would describe it as a non-linearity of the engagement curve, if you follow me. In other words, as you release the clutch pedal, it seems to engage perfectly normally to a point, then grab at the last instant. If you're trying to feather the clutch when it's almost all the way out, you get a chatter as the clutch rapidly engages and disengages.

Two questions:

1) If there was oil on the clutch/pressure plate for any reason, could this cause these symptoms?

2) This is a total shot in the dark, but is the Sachs part number K70029-02 the correct item for this application? I know that heavy-duty clutches with different compositions can be grabby.

Any suggestions most welcome.

Richard