The local JD parts man says the the new spindles with grease fittings only grease the lower bearing. He says the upper bearing is sealed on both sides and the lower one is sealed on the outside. Why would this be the case? Why wouldn't you want to grease both upper and lower bearings. He told me I could buy all lower bearings and be able to grease both on each spindle. Is what he says true? Thanks for any input.