Is your API riveted or welded, I have a couple and one of the real old ones has rivets, that is one squeeker SOB. The welded ones are much better and I haven't had any problems with them squeeking. As for the one with rivets, I have found that a little silicone around the rivets works, but needs to be replaced every year or so. Also, I have had luck with some graphite lubricant, but again needs to be applied more frequently.
Kratz