I've got a '91 L2550 and the two grease fittings on the upper elbow closest to the steering wheel seem to not be taking grease. Also, I was barely able to get the grease gun off of the fitting, so it seems like it was bigger than the other fittings. I cleaned around it as much as I could, but I'm not sure what to do. This is my first Kubota and I bought this used and it was it very good condition, so I want to keep it that way. Suggestions?