Thats... weird. Check to see if the cv can just pop back in. You may need to take it out and tap it with a hammer.

Your bumpstops are setup correctly for your lift, which means the wheels, theoretically, have no more travel then they would stock. You could try extending the upper bumptops which limit your droop. I'm not sure if that is your problem though.

How frequently does this happen? I mean it is not uncommon to break a cv now and then when your spinning tires. But if it happens every single time you go in 4wd then yes something is up.

-Scerb

http://www.scerbfab.com/carb_faq.html