The K-Gro PowerPro is a ridable lawnmower built for K-Mart by MTD and Murray. Released in 1997. Model numbers: 13AL452F120 (38", 12 HP) & 13AQ695H120 (46", 18 HP).
Bill, by that engine size and that you have a gearbox, sounds like a cultivator or a tiller. Gearboxes usually do not take grease, they are filled with a heavy oil.:-)The gearboxes on those usually take SAE 90 or SAE 140 gear box oil. Hope this helps, good luck.