i have used Spicer sealed u-joints since i got into these trucks in 1990,,tried the greasables a few times but they never lasted longer than the sealed Spicers,plus you need to be under your truck weekly to greases these things if you really want them to last,i usually get about 100,000 on them before i change them,,i really love the sealed units on the front axle joints,BUT if you're an offroader,all that is out the window,with the greasables,you can pump in new grease and push out the crap.