Ok, belated posting of "The Findings", or, how to not follow a red herring.
Originally I had a "pop' sound and saw my passenger side 1/2 shaft pop out of the diff.
I attempted to fix what seemed to be a problem (likely coming down the pike, but this issue had yet to arrive at the station). Red herring alert. Had the diff rebuilt into a cast iron 3rd member and housing (GV stuff). The shop somehow kept leaving the known bad side gear in the right side. Sigh.
Ultimately I picked up a used carrier assy sans the r&p. And a spare set of 1/2 shafts.
Had a mechanic friend take pity on me and swap out the side gear (and also did a much better job than did the 'professionals' at setting the r & p mesh, as when they did it it whined, now back to the original 'silent' diff).
He and a buddy did the work at my shop, then we watched as the 1/2 shaft popped out (one of us drove it on a circle and the others observed). The buddy couldn't believe it and asked if I had another 1/2 shaft (after I swapped the hubs around to prove they weren't the culprit). I removed the drivers side inner cv mounting bolts.
And knew immediately what was wrong.
The CV boot was stiff enough that it was holding the cv joint together when it was not forcing itself apart (as it was doing while in 4wd). Darn! Lots of time and effort for a pretty simple problem. What happened? The locking ring had popped out and the slots the rollers rode in had worn a bit in a tapered fashion. Under torque the joint would move a bit apart and the rollers would pop out, transmitting the "pop" through the diff and driving the other cv out of the side gear. Sort of like a politician, make a loud sound about something that is inconsequential to get the crowds attention on it, while doing something insidious. I think this was the original drivers side 1/2 shaft. I guess it earned its keep, living about 200k.
Now to get the steering straight....
And maybe a new mouse motor.
