[cbale2000]

It's worth noting that if you are using Vex gears, running them to wear them down might not be advisable as you would be wearing down the protective ceramic coating and possibly exposing the 7075 aluminum (which is more brittle when exposed compared to standard 6061). The ceramic coating would likely also take longer to wear down than a standard aluminum gear using this process.

If time and cost aren't an issue, I would recommend either using AndyMark gears if you aren't already or remaking the gearbox plates with the 0.002" - 0.003" extra center distance between the gears as others have already suggested (we have always just added the center distance and it works great for us, hardly any noise).