I noticed my 4wd would not auto lock the other day when I needed but the hubs manually locked in 4wd. So I searched on here and found out it is a vacuum leak. I tried the vents to defrost switch when in 4wd but didnt notice any change. The vacuum did run constant while it was in 4wd though. Does this mean it is a line between the valve and hubs? I inspected the hoses from the hub to where they connect on the bracket on the frame but didnt notice any cracks or anything.