Vanagon T3 Syncro mainshaft bearing thrust erosion

Trying to find the cause of mainshaft bearing thrust surface erosion. This bearing has only 40,000 miles. The van has a 2.5L Subaru engine, 173 HP.

Interested if anyone knows the solution to this problem. Some gearboxes have this problem, others do not.

This gearbox was disassembled because the mainshaft bearing became noisy. You could hear it from outside the vehicle, in neutral. Upon disassembly, two problems were found, mainshaft inner race has spalling, and the thrust surface erosion.

This gearbox has always had very clean oil, and has a temperature controlled oil cooling/filtration system (from day1).

There were times that it was driven 80+mph (130kph) for several hours (hundreds of miles). But it was temperature controlled at maximum142F (61C). We knew it was risky to run this 90HP trans at such a high duty cycle - but we wanted to test the “cooled” gearbox under extreme conditions.

We’re disappointed the gearbox did not survive ….. but the erosion problem we found…… is endemic to other gearboxes, even with 90HP. We would like to solve this problem as well.

The question we have is, when you find a gearbox with no thrust surface erosion, are both idler and pinion gears “tight” on the shafts? Or loose as you see in this video?

The other Question we have is “do you know how to prevent the theust surface erosion ?

Thanks for reading and sharing knowledge!!👍🏽👍🏽