Here's a good video. I have been told by people I trust that pinion shaft angle 2-3 degrees down (from the engine/trans shaft center line) is good for a street mopar, and 4 degrees down is good for a street/strip mopar that has the front spring section stiffened, like with clamped front leafs or caltracs. I get confused when measuring the drive shaft angles and then doing all adding and subtracting, so I got a magnetic digital angle guage from Harbor Freight. Zero the guage at the transmission output and then it will read the degrees difference at the pinion yoke. I disconnected the drive shaft to get access. In the horizontal direction, have you measured the thrust angle?
Lots of places sell axle angle shims, including Mancini, Calvert, Holley, and Summit, and as mentioned previously Dr. Diff. In fact, Cass would be the very first person I would contact if I had a vibration problem like yours. [email protected]
This shows the problems when the two angles are not the same, you get vibrations. The joint speeds up and down going the full revolution on an angle so if one joint is changing speed and the other is not quite the same angle it’s a pull and push affair, vibration. Over angled joints absorb HP like crazy.