When you get to higher angles, the balls on the outside/inside of the bend come out of their groove, or at least, don't engage enough to transmit any torque with out damaging the balls/grooves. You end up transmitting the torque thro the balls to the left and right of the bend. Concentrating the load.
Also, all the shuttling in and out wears the balls/grooves very quickly. We have to use special, modified CVDs for XC type vehicles, at huge expense. Not sure exactly what the threshold is, but 18 degrees is sounding alarm bells.
|