If your truck is riding rough, something is wrong. They may not be magic carpet rides 100% of the time, but 80% of the time, the ride should be sublime. Did you just buy this car? How many miles are in it? The ccd is extremely sensitive, and the smallest variables will change the ride characteristics. However, if its rattling and jittery, it may be your mounts. Admittedly, the 4th gen expy/nav was not built well, so they are plagued with extremely noticeable structure issues.
I had a 20 nav, when I bought it, the ride was sublime even with 65k miles, however, the tires were bad so it allowed alot of jitters. Changed out the tires to pirelli scorpions, which helped the handling, but made the ride noticeably harsher.
Also, ford suvs have a huge ride bandwidth. One day, it'll ride smooth as glass, the next day, it'll ride like its a shopping cart. Depending on how long its sitting and outside changes, you may just be experiencing the shocks not performing optimally. What I used to do was put the ccd in sport mode when it would ride rougher, and it would help the ride considerably. Don't ask me why, but it worked.
If all else fails and you just want a smoother ride, grab some 20s and slap em on with new tires. Theres plenty of options to choose, and Amazon has some cheap ones if you dont want oem.