Unless something recently changed, the bearings in the spindles are sealed. The grease zerk is there so the factory could pump some grease into the void between them in order to eliminate condensation. That being said, you should be able to get a grease gun onto them unless your grease gun doesnt have a flex hose or your deck shell is bent, which could pull the zerk low enough that a grease gun can't reach it. If your spindles are making a rough or dry bearing noise, just bolt new spindles on the deck. The only parts of this tractor that are truly greaseable are the front wheel bushings and front axle spindles.