Hi Mik
The damage to the flanks of the gears, the melted bearing cages and the colorful spacer bush are clearly caused by the steel thrust washers.
BUT! The damage to the shaft is caused by insufficient lubrication.
Depending on the situation, the centrifugal lubrication for the needle bearings is not sufficient. If the surfaces have been damaged, the accident takes its course. The damaged area is logically where the load is highest. The designers have placed the oil hole exactly there. But if only a little too hot oil arrives, the lubricating film tears.
The next problem. The needles are relatively small in diameter, they turn really fast and both running surfaces are construction parts (gear and shaft). There is no bearing ring in between. I'm sure that the tolerances in terms of hardness and surface quality on the structural parts are far greater than on standard roller bearings. If the wheel set has play due to wear on the thrust washers, the wheels cant slightly and the needle bearings are loaded on one side. They don't like that.
Which is generally not well known. The Australian Perentie installed an LT95 behind the 3.9 liter ISUZU. Apparently Land Rover Australia was aware of the intermediate shaft problem. I don't mean the thrust washers made of the wrong material, but the wear and tear of the shafts.
This was therefore redesigned for the Perentie. In the permanent version, the wheels run in preloaded standard tapered roller bearings with inner and outer rings. From this point of view alone, it is structurally superior. The Perentie solution fits into the standard gearbox housing. Unfortunately, this version or parts of it is very rare and almost impossible to get in the old world.
Then you have to build it yourself.
greeting
Frank