Just thought I would give a one year update.
The gearbox is very normal sounding. I hear the sound of the motor over the gearbox.
It has turned into my now 16 year old son's ride. He puts 5+ miles a day on it. The set up is virtually maintence free. Everytime I ride my friction drive, I get jealous of the axle mount. The only negative is changing the tire or tube. If you get this set up, get a extra thick tube, fill it with slime and get kevlar tires or inserts.
If you are looking for consistent maintence free setup, this is the ticket.
I never did put the higher gear ratio on. Still sitting in my tool box if anybody wants to buy it. 28mph is fast enough for my son to go.