[Richard]

U-joint working angles and calculating them somewhat confused me a while back. Then I found someone that explained it in a way I understood. Attached a chicken scratch drawing of the way it make sense to me.
You can see I indicated the differential angle as down. Does not make sense right? pinion is pointing up. If you start at the t-case or transmission draw a line through all the components. You can see the line is angled down at all positions. If you start at the differential, it is angled up at all positions. You can do it either way.
U-joint working angles are determined by adding or subtracting the two angles at the joint.
Down/Down or Up/Up you subtract the two
Up/Down or Down/Up you add the two
A CV or cardan joint has two u-joints in it that cancel each other out so the working angle at u-joint on other end of shaft should be at 0 degrees. Probably +or - 1 degree as no working angle is not good as well. Also should add to avoid vibration an attempt to get working angles at both ends of shaft within 1-2 degrees is best.
Maybe this info not asked for but hope it helps someone.