Hey, I checked under my truck and my U-joints are still good, they dont move at all when I try and turn them, however, the clanking in the rear is getting worse and worse. My U-bolts are all good so nothing is moving back and forth, which leads me to believe my Carrier Unit or Ring and Pinion is shot. PLEASE HELP!

 

Only way to help is break out the check book on this one.

 

Pull the diff cover and inspect the gears. If nothing is wrong then at least you get a gear oil change out of the deal.

 

In order to tell if your ring & pinion is worn, you need to pull the cover and check the backlash. ofcourse, you'll need a micrometer and an arm. Hayne's or Chiltons should have the specs on all that.
Also, I had some clanking going on in my '00 Cheby and I thought the same thing because if I was coasting at a slow speed (under 10mph) and jabbed the gas i would get a clunk. When i pulled the cover off and looked inside, my spider gears were completely shot and was allowing the driveshaft to rotate excessively. They were all chewed up and had lots of "worm holes" in the surface. Once that surface wears down, they go pretty quick. Now, I had an open carrier so the replacement was pretty easy and straight forward.
GM dealers wanted $198 for those little spider gears and I ended up buying AAM branded one's(same as used by the dealers, just not branded AAM) for $85 shipped to my door. I don't think the GM packaging is worth that much IMO..lol

Pop the cover and take a look. tell us what you see or better yet take some pics if you can.