On my 4.5, the upper wishbone has two grease fittings that wouldn't take grease. I have replaced the fittings (screw in with nipple) which doesn't help. Oddly enough they have taken grease before, about a year ago. My question is what does this mean in general. Is the bushing worn? Has the grease dried up? Or do I need a better grease gun (mine is hand operated)? There are no other problems with the suspension like noise of uneven tire wear.