I noticed that grease come out of the front left lower ball joint. Could this be a busted ball joint? right lower ball joint seem fine.

 

Is the boot busted or torn? The boot can commonly rip either from impact, rubbing on something, or just wear and dry-rot. The ball joint itself can still be good even with a torn boot, but its only a matter of time before it does give out with no grease and moisture getting in. You can get slip over boots from energy suspension in a universal application (i think, i know most kits come with them) but you have to rig a retention wire to keep the boot where it needs to be and keep the grease in and moisture out. The easiest way to check the joint is to jack up that wheel and then firmly grab the top of the tire from behind and pull it away from the truck towards you. Do this on the bottom too and if you are able to pull the tire and wheel any more than a millimeter or two, then the joint has already started to go. Just went through and replaced all the ball joints on my rig, not too bad of a job once you get the right parts (stupid ebay and advance auto)

 

Thanks for the tips. I'll try that tomorrow after work. The boot looks busted to me.