are completely cracked and there is no grease left. There has not been grease on the wheels - at least not for the past half year, and I have never noticed grease when my parents had it.

My guess is that the boots have been cracked for tens of thousands of miles - at least for over a year now. It's been driven through all sorts of crappy conditions.

Yet, still, I hear nothing from the joints, and I drive pretty hard (fast turns, hard acceleration). I notice nothing unusual about the handling (i.e. steering wheel vibrations, etc.).

How could the joints have lasted this long with the cracked boots?

Regardless, I guess I'm looking at new axles now. :-(