Joe, this is a topic that is somewhat controversial. Some folks will tell you it's not the grease that harms the gears but that the grease attracts dust and junk to stick to the gear and cause the problems, others will say it's the grease itself. I'm talking modern grease here, not old stuff. I would remove any old grease as you just don't know what it is! Triflow is supposedly safe for nylon and plastic gears and is used by a good percentage of people on plastic and nylon gears. Of course, what will happen in 30-40 years? Who knows...