both t-cases run without vacuum. :thumbsup: the vacuum in your old t-case was used to power the CAD in the front axle. You shift the t-case into 4wd, and the vacuum is switched and diverted to the CAD, which engages the funky 2-piece front axle shaft. If you still have a CAD front axle, you can just shim the CAD to be engaged all the time and then everything will work properly. :thumbsup: But make sure you plug the originating vacuum line where it comes out of the engine or you'll have a vacuum leak.