Hahaha, this turned out funny. You old guys are a riot sometimes.
I'm a contractor, I know of many sound deadening materials. My garage ceiling is drywalled, it will have (sparse) pink insulation for the bedroom above, but it won't be nearly enough, as in very often the case with the bedrooms over garages in Canada (bedrooms always cold due to insufficient insulation and vapour barrier. (Good builders spray foam them now... but not many). My one car garage is not getting gutted to put roxul in the ceiling. Way too much stuff in there now... shoulda done it when I moved in. I heat my garage with a hot dawg gas unit furnace. I sprayed foam onto the walls I could access, but not the ceiling. So, insulation is not an easy option. The other issue is vibration transfer. I put the lathe (bench top) on thick industrial rubber mats, that helped big time.
I've adjusted the banjo many times and I feel it is optimal. I can coat those gears in grease, and they shut up for a little while. Till the grease works it's way off the teeth and then it's noisy again. We are just talking about regular gear noise. No significant wear or back lash or clinking between gears. Just the regular grind and hum of gears. The gear box is the same.
I was just wondering if there was a grease I could use that would stay in the teeth longer than the blue stuff I'm using that's actually meant for my 1964 Robins & Myers boat sized 2 hp compressor motor...
But thanks guys, this was entertaining.