Take it off and randomly install some odd sized washers behind it.
Also you can cut some off the teeth off with a dremel tool, every other one should be suficient, you don't really need all those teeth anyway do you? besides, might be a good way to shed some extra weight from your engine
Once you reinstall the gear drive with the afore mentioned mods, it should be loud enough to satisfy your need for a loud gear drive, you might even get some of those "what the hell is that!" looks from bystanders

John