Need help with gear reduction

I have been using my CNC router for a couple of years with great satisfaction despite some blatant violations of sensible design. The most obvious short cut is the absence of any kind of gear reduction. In all three axes I have a small pinion on the motor shaft meshed directly with a rack. My motors are probably bigger than they need to be at 640oz. Everything works well despite the aforementioned configuration that certainly isn't a good recipe for resolution and quiet operation. So I want to take off enough time from project building to add a gear reduction. I'm especially eager to get rid of the buzzing that goes along with the motors having to run so slowly. I usually run them at about 60ipm. The buzzing disappears for the most part at 420ipm, a factor of 7x. Before I start ordering pulleys and belts I wanted to see if anyone knew of any adjustments that might help so that I didn't have to make such a drastic change. I know there are some screws on the Geckos that can be turned but I don't dare do so without knowing what they do. I was really looking forward to the Mach seminar but unfortunately it got canceled. Any help will be appreciated.

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