Didn't rotate the gear. Of course it could have been done by the previous owner. We've only had it for about 30 years :) I was about 10 yrs old when my dad bought it. He still uses it all the time.
I can't visualize what you mean by the front axle trailing center shaft. Can you explain with more detail. It's been a year since I took it apart. When I took it apart, I put it back just like I found it. If it was wrong I would not have known.
As soon as I get a chance I will take it apart and look at it again.
So, just remove the upper gear from the shaft and add shims to cause it to mesh tighter in the lower gear?