Welcome to the club. I am starting my 2nd full season with the F3060. They are good machines. Mine has about 2500 hours on the clock and seems to be running like a top. Mine on the trailer to bring home:
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Concerning the rear axle lube, the differential is separate from the outer gear cases. Draining the outer cases can be a little problematic, if the Allen drain plugs are rounded out. Both of mine were. I used an appropriately sized Torx bit and pounded into the stripped Allen recess on the plug. I was able to get enough purchase for the plug to turn out. I replaced with new plugs.
Concerning the hydraulics for the blade, I am lucky enough to have the hydraulic kit on mine. I have not researched finding a blade for it, but I am pretty sure I am not that lucky to find one. Fortunately our winters are usually not that snowy to need one, but it would be sweet to have one when it does snow.
Enjoy that diesel mower!
Doug