Ask 10 people get 10 different answers, lol! This thread proves that point. For one piece driveshafts I use equal but opposite angles. If the trans points down three degrees (-3) then I point the rearend up 3 degrees (3), the angles are equal but opposite. Now if the trans points up it would be the opposite of what was stated above. A two piece is a little more difficult to explain, but Max is right, there is a great article on
www.airridetalk.com. With a 4-link and the power that people are using in the daily drivers I wouldn't even worry about preloading the pinion angle. Double cardan u-joints like that used in lifted trucks are setup a little different also.