I am going to start off by saying I am very well aware that the gears inside the Bachmann Climax have issues. (They should not, but they do...)

However - I was under the impression it was the gears in the trucks, not the gearbox itself.
The cylinders spin, but zero driveshaft movement at all. I have pulled off the ash-pan, but all the gears I could see without further disassembly appear ok, with no slipping detected.

Is this also a "known issue" with these models?
Is mine a fluke?

Is this something Bachmann could fix, though OOW, for the standard fee?
Is my getting it from a vendor at a train show, as NOS, going to affect the repair, as there is no receipt? (This vendor, you pay cash, you do not get a receipt to speak of... But you get a better price with cash...)

I am confident I could have replaced the truck gears if they cracked on me, but higher up in the gearbox?? Not so confident....
Could there be something I am missing? I only attacked it from below, as that was the easiest to get to based on the schematics... How would I get at the top of the gearbox?

If it was the top of the gearbox, would the cylinders still spin?

I am sure it is not a lubrication issue, as the factory lubrication on this one is very heavy, to the point of being everywhere and needing much of it removed.

Appreciate any and all help provided.