My 2004 F250 Superduty Lariat has a vacuum problem. The automatic hubs do not lock in when I select 4WD. I can feel the drivetrain kick in, but the hubs don't. I couldn't turn them to do it manually, but I fixed that tonight. Now, I noticed that when I select 4WD, it works but my blower/vents changes directing the flow out the defroster vents. I'm sure this is a vacuum problem, but where do I look. I checked the lines from the frame to the back side of the spindles and all looks good. Any help out there?
Mark
Mark