so what if there's no grease on the outside of the boot anywhere but the boot depresses pretty good like nothings in there. I do know that if that happens the cv should click at least but it's just a vibration so I'm stumped...and as far as the 4wd drive shaft I haven't check it out

 

Grease gotta go somewhere and it is too heavy to just drip down on the ground.

It will only click on turns...in a front wheel drive car because the ***** are jumping around in the cage.
I still holdfast to your tires being the cause.

 

So if it the tires what would fix it? get a new one? or maybe balance then alignment?

 

This is crazy I just got in my truck and heard the same exact noise and pulled over to Google what it could be. Ran into this thread. I don't have a four-wheel drive tho I have a 08 Chevy Silverado 1500. I just got new tires on new hubs brakes rotors put on it I literally spent $3,000 when I was just trying to buy tires. Something is off I can feel it under my feet.Everybody thinks I'm crazy but I know my truck and it does not feel okay. It's hard to explain but when I read your thread it's exactly what's happening with mine. It sounds crazy but I'm so paranoid that one of my tires are going to break off or the axles has a crack. I know I might be paranoid but I know my truck and something's not right in the bottom of my feet whatever is under there underneath the truck. If you find out what it is can you let me know. Sorry for the rambling I was just kind of excited that I found this thread because I couldn't explain it but what you were saying explained it for me you know what I was talking about. I hope that you figure it out because I'm going to wait on you to see if you did so I can figure mine out too. LOL hope your day is going great.