I agree, not a very stout design. There is a bit of movement, but hopefully the oil film takes care of it. My truck had evidence that the u-joint had completely failed, gouging the inside of the torque tube ball. I have the original gouged up ball, another I got from a stovebolter, and another NOS ball housing that I put on the truck. I'll keep my fingers crossed that the u-joint doesn't blow up, but it should outlast me. Maybe inspect every few thousand miles.
