I don't know if its me just noticing it for the first time, but I was tightening up the bolts on my wheel earlier and as it span free in the air and is it span slowly I could hear (what sounded like gears) occasionally clicking together. I did notice that there was a grease explosion from around the bottom of the the CV boot. Could this be from there, or is it a normal sound from the gear box when you spin the wheel? 

Does it make a noise when driven on full lock?

Literally it only happened as I span the wheel gently and slowly. If it was fast then there was no noise.

Try it on full lock. That will tell you if the dry CV is damaged in any way.