Locking the CAD

Would it be a good idea to put a bushing in the CAD shift fork to make the front axle's locked together all the time? The vacuum is unreliable, and a posi lok is $150. Is this a good idea?

Only you can decide if it's a good idea for you, but it's not a terrible idea. Several people have manually shifted theirs to the engaged position and shimmed it with washers to keep it that way. Chrysler stopped using the disconnect on the XJs in 1991, so by locking it in the engaged position you are just emulating the factory setup of the newer years.

Guess it wouldn't hurt to try it then, I can always undo it if I don't like it.