quick vocab lesson... your truck is incapable of "full-time 4wd". that particular phrase is associated with systems that allow 4wd use on dry pavement. Yours is a "part-time 4wd" where you should not use 4wd on anything but slippery surfaces (gravel, dirt, snow, etc).
that all being said, the t-case lever controls 2wd-4wd. :thumbsup: as long as it is in 2wd, your truck is in 2wd. The CAD controls whether or not the front wheels get anything from the t-case after you've shifted the t-case into 4wd. Jeep eventually did away with the CAD system completely in the early 90s. It didn't give any measurable improvements in anything and was a pain in the butt to keep working properly.
One thing that may pop up after locking the CAD is vibrations from your front driveshaft if the U-joints are bad. But if they are bad, you should be replacing them anyways. :D