how to tell if you have a bad carrier bearing?

Okay I have never ever looked at the carrier bearing before today on my truck but noticed I can push it up and down and it moves much more then I would have thought it to. What do they look like when new? how long do they typically last ?? it does not look that bad to replace. ( I use to rebuild Porsche engines) I have 84,000 miles on the truck and tow a little with it and just put air bags in it.

 

mb911,
I have the same question, but I have a 3" lift on my dbl. cab. I had a semi-major vibration/sqealling underneath the cab and narrowed it down to the carrier bearing/driveshaft angle. I dropped the carrier bearing 1/2" and the vibe went away But, now should I replace the bearing and maybe U-joints while I'm down there?