Multiple Double Cardan Joints
Some late model Chevy S-10 trucks, and perhaps other GM/Chevy trucks that utilize a two piece drive shaft will have a single u-joint connecting the transmission and first shaft, while the first and second shaft and second shaft and pinion will be connected with CV joints. This is good news for those that are worried about pinion angles when installing a custom rear suspension or link setup.

Recall from before, that two objects connected with a CV joint will have the same speed as one another. Lets take that idea and run with it. The pinion and second shaft are connected with a CV joint. This means that whatever speed the second shaft rotates at, the pinion will rotate the same.

The first shaft and second shaft are also connected with a CV joint, so the first and second shafts will rotate at the same speed.

Thus, the first shaft and pinion will rotate at the same speed (Note, that regardless of the angle of the second shaft and pinion, they will still both rotate at the same speed as the first shaft (the property of the CV joint).

Since the pinion and first shaft will rotate at the same speed, all you need to do is make the operating angle between the transmission and first shaft as small as possible. Remember that a 0° will offer the u-joint no lubrication, so instead, set the operating angle between the two at 1-2°. (If the transmission points down towards the rear end at 3°, then point the first shaft down 1° [This can be done with spacers under the transmission and carrier bearing]). Since the angle between the first shaft and transmission will only slightly change under acceleration, regardless of the height or angle of your rearend and pinion, it will always rotate at the speed of the first shaft.

Setting The Angle
With that all said, you might wonder "Well then what do I set my pinion angle to at ride height?" Its quite simple.

If you have a single driveshaft with a single u-joint on each end, simply set the pinion angle opposite of the transmission output angle. If your transmission points down towards the rear of the vehicle at 3°, then point your pinion up towards the front of the vehicle at 3°.

If you have multiple shafts with all single u-joints, you have to do a little math. Take the first operating angle, then subtract the second operating angle, and that is what the operating angle between the pinion and second shaft needs to be.

If you have a multiple shaft setup with cv joints, its really easy. Set it so that the operating angle between the second shaft and pinion is about 2°. See the images for a visual idea of what I am talking about.

Now that I've explained all of this, I hope I have aleviated some of your confusion, and hopefully you should have some sort of grasp on the idea and concepts here.