Driveshaft intermediate bearing

[Simon_P]

Yes quite normal - What you are describing is the physics of an angular contact ball bearing.

For the radial play 1 micron or wear gives 1 micron of play.
For the angular movement trigonometry comes into play the 1 micron is a change in "height" the displacement is tangential to the "height" and at small angles either side approximates to the same thing (Sin Theta etc if I remember correctly) so the resultant displacement is greater than the wear. You are then amplifying a small angular movement by the length of the shaft.

[Giniw]

So, the new bearing is now pressed in, and the intermediate shaft back in the car. The Elan is on its wheels
I haven't had the time to test drive it, but the new bearing is definitely much tighter than the original one.
As I said the original one had no radial play, a bit of axial play, and quite a bit of angular play.
The new one however has no play at all in any direction (I mean, none that I can feel by jiggling it by hand like I did with the old one).

Next step is to change my RHS front lower link, but it will test drive it like before and see if it address that vibration ...

[Giniw]

So, I test drove the Elan for about 10 miles last Sunday and apparently it doesn't vibrate any more despite me flooring it in second and third on many occasions ^^
I hope it will last but apparently the bearing change cured the problem!
(It's a pity it's due to MOT and I still have a few things to address before, so I cannot drive it on a daily basis to confirm the problem is really gone. But I really think it is, which is rather good news!)