Cool, I can't open the scene in Mod Tool to check it out, can you post an image of the schematic view please?
I'm not familiar with Maya but I assume Locators are the same as nulls in XSI and Aim constraints are the same as Direction constraints in XSI.
In the video he starts with 3 parts, the left part (input shaft), joint (journal cross) and right part (output shaft)
Then freezes the transforms which puts the center of each in the same position
Then he makes the journal cross a child of the input shaft
Then he creates 2 locators (nulls) and moves the upLocator (null1) to the side and the aimLocator (null2) behind the output shaft
Then he makes null1 a child of the input shaft as an upvector for the journal cross
Then direction constrains the journal cross to null2
and finally direction constrains the output shaft to null2
So far this all works when it rotates in place or when I move null2 up and down while not in motion, but the journal cross rotation breaks when trying to move null2 while the animation is playing.
I'm obviously messing up a step here and I think it has to do with the upvector not working properly.
Any help here is appreciated.
If someone would be so kind and load pooby's scene in Softimage and take a couple of screenshots of the objects in the viewport and schematic view so I can reproduce it in Mod Tool 7.5 that would be great!