I have a gear box on my JD grindermixer on the bottom of the mixer that leaks. I read on here that it may be a canidate for corn head grease rather than the 90wt oil. Do I drain the oil out first or do I just pump the grease in with the oil? How will I know when I have enough grease in the gear box? It has a check plug in the side and I just add a cup or so of oil to that leval every 4 or 5 times I use it now. I have never used this type of grease but I wouldn't think I would want to pump the gear box full of it. I picked up a couple of cartrages of it at my I-H dealer and just trying to figure out how to go about it properly. Any helpful advice on the matter would be appreciated.