Pinion angle help.

Update, I got the car back in shop. Just out of curiosity and some extra time, I just pulled the 8 3/4 rear out. I put the 7 1/4 rear end back in. And measured the pinion angle and found it to be set at +3 ( 3 degrees up ). I got a set of 3 degree pinion shims and out of curiosity put them under the front of the 8 3/4 and rechecked the pinion angle, it is now at 0 degrees. I put everything together and took the car out for a short test drive. I found out that the noise it was making was still there BUT one half to 2/3's as loud. Maybe I going the right way with pinion angel. ??? I didn't re-check the transmission angle.