With engine out, I removed the gearbox and spent a lot of time removing the decades worth of dirt & oil buildup. At least an inch thick in some places. Several coats of degreaser and a high pressure water blaster removed a lot, but not all. Wire cup on grinder is next, this weekend.
Once the top cover was unbolted and gear oil drained, I flushed the case with petrol. When cleaned out a bit, the gears all looked in very good condition. I couldn't find any evidence of damage. No metal bits in the oil and everything inside is quite rust free.
I plan to replace both main shaft bearings and any seals, but everything else inside can remain untouched. There was obvious signs of considerable oil leakage both fore & aft of main shaft, so seal replacement is a must.
The gear shifter assembly was stuck fast and I had feared what I would find inside the gearbox. As it turned out, the reason was simply that the selector slides were held in place with light surface rust. They are now moving again, thanks to WD40.
The parts manual will be studied this weekend and the desired part numbers will be emailed to Ross Prince at Hervey Bay. He'll have all the stuff I need!
Ironically, the gearbox is NOT the main focus at present. The chassis is next on the list for refurbishment, but until I can find a pair of axles & some wheels to put under it, I can't make it suitably mobile for sending to the sandblasting place in town. I'll call the local scrappy next week, they sometimes get junk trailers & might have some usable axles and wheels.
P.S: What is the deal with the little 'hydraulic' line from the throw-out bearing to top of gearbox case??
Does it carry lubricant to/from the bearing, and if so, is it automatic or does it require maintenance???