Well, let's see.
I drove it at a snail's pace about 3/4 km yesterday...it vibrated and 'ground' its way along, after the first 50 feet or so.... This morning I drove it back here...in reverse...not a sound, only a few puzzled looks! Removed the drain plug and found what you see on the attached thumbnail (and apologies for the size of the pic's). Those are metal filings of the type you might use in science class to demonstrate magnetic fields...about 750 metres worth!
I took the chaincase apart again today...the inside of the outer reverse gear (see thumbnail) shows what looks to my untutored eye as a distinct wear pattern on the outer edge...all shiny and new...the few marks around the pin-holes in the centre strike me as normal wear.
And the chain looks to have some wear on it, too...along its outer edge, looks like...and the link pins are wearing, too, I think...(see thmbnl).
And the open case looks fine, not that you can tell much from that, I suppose...the blue is the locktite.
Both upper and lower bearings are solidly in place and kept there by their flanges...the jack and drive shafts look to be in place as much as they ever were. The adjuster is manual...I just set it finger tight and add a slight nudge with a wrench and set it in place. The track is adjusted according to AC specs...from the service manual. My straightedge says the upper and lower gears are aligned.
The large thrust washer on the drive axle is fine...I thought if it were twisted somehow it would cause a problem, but I couldn't get a .004" feeler gauge underneath it anywhere with it on a flat steel surface.
The initial problem, I think, came about when the bolt in the lower gears backed off some...altho I had to use a socket to remove it. Initially there was this pulsating that was more felt than heard and which then over the course of three hours or so became 'heard'...and finally on the leg home there was a light grinding sound, but nothing like what I heard last evening when I drove it (against my better judgement, I don't mind saying) home.
I don't mean to kick this around so much, but I have no other source of AC insight and experience...no dealer anywhere near (air freight to the nearest dealer's about $1200
I'm thinking of reinstalling the original bearing...bearing was fine but I replaced all four since the upper chaincase bearing had some roughness when turned and PTO jackshaft bearings was in bad shape.
Thanks for the replies guys...really appreciate your time.
But...if you think of anything else!!