If you had that bad of a vibration you needed to rebuild your shaft anyhow. The CAD was done away with in later years because it is a crappy design. It will only take one time for it not to work when you need it most, when you will be kicking yourself for not deleting it.
Just think if you dive head first into a hole thinking your front axle is locked in. You get about rocker deep and all of a sudden you realize you are nothing more than a 2WD truck and you're now stuck. You will have to get pulled out, winch yourself out, or go SCUBA diving to fix your none working CAD.
I always lock them over because that has happened to me. Now I never, ever wheel alone.