Original Grey Technic motor from 1977: 6216a

[Jens Bauer]

s/6216me --> u9376
s/6216mf --> u93777 and u9377 (split platic and metal section or reuse u9375)
6216a --> u9372c02

Unfortunately, the metal-axle differ; the 1977 variant is slightly shorter because otherwise it would be visible from the outside.
(I actually made 6216mf '0.1' shorter, but it could be a much lower number).
If u9375 is to be re-used, then I think u9375 needs to be slightly shorter (just a fraction of its current length), so that the axle will cover the metallic surface. By a fraction, I mean something like 1/1000000mm would be fine, because the rendering engine shouldn't be as picky as we humans, except for possible rounding-errors, so beware of this.
I also think your plastic axle would need a modification, eg. making a cylindrical hole all the way through the axle, so the metallic axle would be visible.