Pinion angle - have a vibration

I fought this problem also and after some research I found this:

http://www.moparts.org/Tech/Archive/axle/8.html

At the end of the article it also gives you the angles using different rear end set-ups. I ended up happy with my pinion angle 1 1/2 degrees lower than my trans angle. I guess, depending on how stiff your springs are, the amount your pinion rises (under load) probably determines how much you should be "below" the trans angle. If I read this article correctly what you want is for your angles to be the same when the rear is under load (centerline of pinion parallel to centerline of trans). Unless your rear end is mounted completely solid it should rise (the pinion anyway) under load, the amount it rises will vary with each different set-up.

Hope this helps.
LOVE MY 2004R!!!!!
Treblig