I had the front end up on ramps, therefore that explains why so much fluid was present in the tailshaft.
The bit about the numbers still baffles me, though. As I rotate the fixture around to the different positions, I don't visually see anything different in how it "sits" in the recess provided.
And there is no visible difference on the inside of the thing either.
Now, of course, a speedo pinion gear with a DIFFERENT number of teeth, may very well indeed engage the tailshaft gear more deeper (or shallower if that be the case).
But I just don't see how any particular setting would affect the specific gear that's in there now.
Just another one of "life's mysteries", I'll have to learn to live with, I suppose
Thanks for the response