Rear axle pops

What is your question?

I have a 06 sportage kia, I been having problems with rear axle for some reason, when I make a turn to either side the rear axle makes a poping sound. also when I go on revers, an turn. I removed the drive line so that I could tow it. Do the 4wd vechil. are suppost to be in some kind of allignment with the rear and the front for the gears to work together. Please help.