Yeah, I found that out the hard way. Ziiing, no mo locomotion.
And you are right, you cant tell with the naked rye. Not even with a magnifying glass.
But hey, since you know and understand about that problem, and have those great m/s pics, which clearly show the code system on the rear ends of the shafts; do you also have pics of the matching planetary code system. I have parts to build at least 6, 904s, but am afraid to put them together for fear of warranty returns due to this exact problem.