My old Kenmores have this gear box filled with grease, too. If it looks fairly clean, I've always just replaced part of it with Singer lube. And, if it's really crummy, I replace all of it with Singer lube! I've done tons of searches trying to find out exactly what kind of grease is in there to no avail. So, I just used the Singer lubricant. My machines sew beautifully & quietly so I'm guessing it works! Actually since you're just greasing gears, any grease that doesn't harden over time (or melt down to a liquid & leak past the gasket) should be fine....at least that's what I'm thinking!