I have an intermittent problem whereby the thing screams at me from time to time. Did it twice yesterday, but hasn't done it for over 12 months before. I suspect lack of use has something to do with it.
A reputable gentlemen and expert in these matters advised a course of action that involves removing the inner flex shaft, cleaning, soaking in ATF, cleaning again, re-soaking in ATF then reinstalling. (ATF has some quite aggressive cleaning properties).
I will give this a try before I try to pull the speedo. The lacerations from a failed (5 hour) effort at replacing a tacho for a friend have only just healed, but the mental scars run deep.
JH