Some drive axles are hollow, so if you're going to hold them in a vise during CV service, be careful not to overtighten. After cleaning the grease out of a joint that you suspect to be faulty, examine the working surfaces carefully. Excessive wear will show up as scoring, pitting, or brinelling. Look for cracks, too. Highly polished or dull areas, or a blue tint aren't sufficient cause for replacement.
CVs absolutely require special extreme-pressure lubricant.
In most cases, packets of the proper grease are supplied with new joints or boots. Never use ordinary chassis or wheel bearing grease. Since considerable labor is involved in removing and reinstalling drive axles for CV joint service, it's usually poor economy to reuse the old boots. New ones will provide dependable protection for those expensive joints. If a boot is collapsed after installation, pop it back into its normal shape by inserting a dull, narrow screwdriver under the small end to relieve the vacuum.