My Craftsman riding mower is getting real noisy in the rear end. It's the 15hp model with Kohler engine and a transaxle. The noise is present even if you let the mower coast down a slope with the tranny in neutral. I checked the fluid level and added some 90 wt. trans oil since it was a little low, but the noise is getting worse. Are there wheel bearings on the axle or am I going to have to replace the whole transaxle which is probably not worth the effort or cost. The mower is about six years old, but only has about 200 hours, if that much. Suggestions?