Several years ago, on my gas engine 2003 F350, I replaced my auto locking hubs with Warn manual hubs.
Recently I am experiencing the dreaded A/C defaulting to the defrost vents under low vacuum conditions due to a vacuum leak. I have isolated the leak/low vacuum issue to the auto locking hub system "vacuum solenoid". Is this piece still necessary with manual hubs? I was under the impression that the hub vacuum system was specifically for the auto hub system.