Marlin, I won't respond to your insults because I'm not interested in quarreling with someone I don't know, who lives 10,000 km from me and whom I will never meet; on the other hand I like technical discussions, especially with a professional.
After all your explanations it is obvious that your bearings are perfect, much more precise than anything I could ever make myself BUT, because there is always a BUT, how precise is the position of the end of the input shaft relative to the bearing housing in the crankshaft?
This position depends on:
- the concentricity of the different bearing seats of the shaft
- the perpendicularity of the axis of the bearing housings in the gearbox housings in relation to its support surface on the clutch bell
- The concentricity of the different bearings
- The position of the housing axis in relation to the centering of the gearbox housing with the clutch bell
- the position of the two centering pins in the clutch bell
- the parallelism between the both support faces of the clutch bell
- the positioning of the centering pins in the engine block in relation to the axis of the crankshaft mean bearings hoping that the bearings have never been realigned
- the perpendicularity of the axis of the main bearings in relation to the support surface of the block
- the concentricity of the bearing housing in relation to the crankshaft bearings.
- anything I may have forgotten......
All these criteria can not be perfect, they all have a small error, tiny but not zero. We can hope that, statistically, certain position errors compensate for each other, but they can also add up.
I obviously don't know the different manufacturing tolerances at the time, whether at Ford or ZF and I therefore cannot make an exact calculation, but I know they were not of the order of 10 /thousandth of an inch and I think we can estimate the final result at 1 or more tenths of mm, or 1 or more hundredths of an inch.
So your bearing is precise to less than one 10/Thousandth of an inch, I readily believe you, but it will receive the nose of the shaft which can be off-centered by one or more hundredths of an inch.
So, certainly the end of the shaft will not vibrate and that is very important, but it will still undergo alternating flexions which could cause vibrations elsewhere along the shaft because the axis of your bearing will not be perfectly aligned with the axis of the input shaft which, moreover, can have a slight angle in relation to the bore of your bearing. I suppose that it was designed by ZF for support this and it's why I wonder about the benefit of such perfect precision on just one of the parts of such a complex assembly.
I'm like mechanical assemblies, I'm not perfect, I can screw up, you obviously have the right to disagree with me and we can discuss our points of view between engineers in good faith.