Air blows from the panel then defrost then floor without me touching it.

If I set the panel to "VENT" it'll blow through the vent until I begin to climb an incline then it'll blow through the defrost and then floor. It does this all the while the control is set on "VENT". It eventually blows back through the vents once I drive on a level surface and basically have the engine under a light load.

I also noticed last winter my xfer case popped out of 4WD several times under load. The lever itself did not move..the xfer case basically popped itself into neutral forcing me to pull over, shift into neutral and then re-engage the xfer case. I have a NP231 Command Trac setup.

I'm thinking vacuum I have a vacuum issue..what do you guys think?

Ghost maybe?

It sounds like some kind of vacuum issue if you have had both of those issues. Not sure how incline/decline would affect it though other than if it was possible, and this is a total shot in the dark, for there to be water in the booster or something. :dunno:

It probably switches on an incline due to the larger throttle input. You've got a vacuum leak causing the issues. The vacuum canister can crack, causing troubles - that'd be the first place I'd start.

check for cracked vacuum lines especially near the battery. the check valve could be bad too

I'm undergoing this same issue. When I throttle the Airflow shifts to defrost and when I'm not powering down it goes back to the panel vents.

I previously got only Defrost Airflow. I recently found a vacuum line near the car battery and the underside had what looked like a small burn mark. I wrapped it in duct tape and that got my vents working. Now even with that line wrapped, I suspect the duct tape isn't adequate or I have a second leak somewhere.

Can vacuum lines be repaired (rube goldberg'd, duct tape, etc) or do they have to be replaced?

Repair is possible on plastic hardline, but replacement is a MUCH better alternative....

It IS a vacuum issue.

The reason it cuts out on an incline is because you're accelerating. When you accelerate, vacuum goes away, unless you're running off the vacuum in your reservoir (which you can't, cause you have a leak). When you let up on the gas (level, or less load) vacuum comes back.

You more than likely have a vacuum leak in the hoses running under your battery tray due to corrosion. Check the lines, you can repair, using a small section of line and some rubber line. But since the small lines cost about 50 cents a foot it's a good idea to replace the whole line.

Although duct tape is a wonderful invention it's ridiculous to not replace the lines (all of them if you have to). You'll be glad you did.