I just finished reinstalling it. It does look as though it's clocked right, if I understand what you're referring to
What he means:
Both u-joints need to be working in the same plane. Turn the driveshaft so that one set of cups is in a straight line across pointing at each side of the frame, parallel to the ground, and the other 2 cups on that joint would be in a line 90* to the ground. Then look at the other u-joint and the cups need to be in the same position as the other u-joint.
This is easy to get wrong on a 2 piece slip joint type driveshaft like on some 4wd that the front yoke does not slide into the trans like a chevy car. If they pulled apart the slip and didn't get both joints in line, it will vibrate as the 2 joints fight each other as it turns.
Or if it's a one piece shaft that was cut & welded and not indexed correctly before welding.
Cross type joints do wierd things as the angles increase. If you could put the worlds most accurate tachometer on both ends of a driveshaft with both joints running with no pinion or trans angle, the speed would be constant on the rearend compared to the input speed. But if the joints start running with an angle, a tach would show the trans is turning a constant stable speed, BUT the rear pinion would actually speed up and slow down as the 4 crosses rotate one revolution.
That's what happens when you lock the front hubs and go into 4wd on bare tar, then cramp the wheels....The front end goes nuts as those joints do the speed-up slow-down as they turn. That was eliminated on early wartime jeeps that had constant velocity joints instead of cross type, because those jeeps had no lock out hubs. Hence the name "constant velocity" as this design enables the driven object to have a consistant speed with the drive flange.
To the best of my knowledge, a cross type driveshaft should also have matching pinion & trans angles in a perfect world, but have seen very few 4wds that did.