Weekend update 251,721
Broke my rear diff and replaced it.
It started making a ticking noise every 4th or 5th revolution under load, not coast, 2-3 week ago. That got progressively worse until it ticked with every revolution, getting progressively worse until it fractured.
Based on the progression I keep it was coming so I took it easy until it failed and stayed close to home. The failure happened within 5-10 miles of me first noticing the noise.
Based on the initial intermittency of the noise, and it's progression, I believe a pinion bearing failure led to this
Once I diagnosed it with a mechanic's stethoscope (20" 3/8 socket extension to the ear) I ordered a replacement from ECGS, it arrived mid-last week.
I called a tow truck to take me to my buddy's house so I could change the diff. I can't do things as involved as that at my apartment. AAA easy.
Driving it up the ramp was sad.
Once I got it off the truck I drained the diff, not much debris came out nor was much on the magnet. Once I pulled the 3rd member I found several 2-3" sections of the pinion gear teeth at the bottom of the housing, debris of varying size. Many of the smaller pieces were ring gear chunks.
I mopped and rinsed the entire housing, even removing the inner splash guards and flushed them with brake cleaner.
I did the same with the housing and replaced the gasket
Install was pretty easy and the opposite of removal. Torqued everything to spec and filled the diff with Lucas 85W 140. The whole exercise took 6 hours.
Broke the gears in with 4 successive drives between 15-20 miles each, letting the diff cool in (completely) between drives.
First drive was 15.1 miles city / suburbs, 30-40 mph max. Second drive was 18.3 city / hwy, 60-70 mph max. Next two drives averaged 14-15 miles each and were basically the same as the second - all 4 drives totaled 63.7 miles; ending mileage 251,785