Noticed all of these little vac tubes are disintegrated. What are they for? And is there a part # to replacements?

 

That looks like the IWE solenoid-locking hubs control. I've not had to fix one like that but I would try to slip a piece of vacuum line over the plastic tube and put it on solenoid to replace rubber fitting.

 

I believe you are correct. All tube are just crumbling apart in all locations. I believe this is the replacement part. So if there's no vacum does that mean the 4wd isn't engaging?

 

Vacuum going through the soloniod disconnects the 4wd hubs, with the line broken off your hubs will be locked to your axel shafts but you are not in 4wd till you put the selector in 4wd. You can drive around like that till you get the part, but plug your line off the solonoid or pull the wire because it will be a vacuum leak to your engine.