Thanks for the advice. I've looked at the parts diagram. The problem bearing is the center blade. Do I need to drop the cutting deck down from the main frame and slide it out, or can it be replaced while still installed on the mower? I'm assuming I need to hold the blade securely and remove the nut on the top, and then remove the split ring to free up the bearings? I've not managed to find any specific instructions about removing and replacing these bearings.