I finally got it all wrapped up! I am by no means good at this, but I ended up taking the carrier / pinion out at least 25 times - one one Saturday I had the whole thing apart and together at least seven times.
I believe my core problem was that the pinion bearing became worn. This allowed play in the pinion gear itself, and poor engagement with the ring gear. As I noticed earlier in this thread, there was no backlash in the pinion at all, and it would flop around by hand.
The "fix" for me was to replace the pinion bearings and races, then choose the proper pinion shims and carrier shims - reusing my factory gears. In my case the pinion shim needed to be reduced from what the factory was - I think I went from 0.023 to 0.012"
Things I learned along the way:
- You have to make a setup bearing for the pinion gear. Order two of the same bearings (i.e. same manufacturer) and use a die grinder to expand one so that it slips over the pinion easily. You'll use this to change the pinion shims over and over again.
- Get the pinion shim / depth correct before worrying about the carrier shims. This is a bit hard to do as you need to read the gear patterns along the way, but focus on pinion shims first.
- mix gear oil into the gear paint. I think I was putting 3/4 gear oil to 1/4 paint. This make the paint go on better, and makes the patterns much easier to read. When I was using the paint straight I could barely see what was going on yellow everywhere!
- drive side patterns are way more important than coast side. Get the drive side as good as possible and run it.
- with used gears (like I was doing), you may never get a perfect pattern. In an ideal world, you would want to get the pattern back to the way it was from the factory, since these are "mated gears". No possible in my situation. I agonized over the pattern, and got a pretty good one, but not as good as the ones you see in the videos.
At the end of the day, it's not really that difficult. It's intimidating, but I took my time and did it dozens of times until I got pretty good at setting things up. I've got over 125 miles on it, including quite a bit if highway, and it is sooooo much quieter now.
Great videos to watch: