if 3 feels notchy.. and 2 is free.. if you hold the pinion cup, and hold the outdrives, can you feel a backlash space in the pinion cup as you wiggle it back and forth?

not in and out.. your not trying to gauge the space between the pinion cup and the bearing and the pinion gear. it should be tight already. your trying to feel the space between the pinion gear, and the ring gear on the diff.

3 on one side is noisy. but turns without binding, your good. if you feel high spots, or to a point where it takes noticable effort to turn past that rough spot, go back to 2 and 2. when i was 2 and 2, you could see atleast 1hour, maybe 2 in the backlash. thats looose. i went 3/1 shims, and it was noisy again, but 0 backlash. eventually i replaced the r/p but got away for another gallon.