Cruise control and 4x4 have stopped working

[99Lifted]

So I did the plenum repair kit to my truck and everything about that worked fine, up until Friday night. Some of my buddies and I where out mudding and came up to a hill that needed 4 wheel drive to get up. No problem I put it in 4 wheel drive and it doesnt actuate, im like tf. So I take it home since it was late already. I started messing with it saturday and sunday trying to figure out what the problem is. I followed the tsb ( Diagnosing 4WD Engagement Problems on Dodge Ram pickups ) and no luck. The drive shaft doesnt spin when in 4x4 . But I have no vacuum coming from my transfer case at the vacuum switch. So I have replaced it and no luck. Now today I was driving on the interstate tried to use the cruise control, light came on but it wouldn't hold the speed. So now im lost, is their any way these two systems are connected? Any advice would be nice.

Also my vacuum lines all look fine for both the cruise control and 4x4.

TLDR: 4x4 and cruise control have stopped working. For the 4x4: driveshaft doesnt spin when engaged in 4L or 4H, but wheels still spin, no vacuum coming from vacuum switch even though I replaced it, 4x4 light does light up when truck starts. For cruise control: cruise button lights up when cruise button is pressed but doesnt hold speed.

 

[yoda]

There is a vacuum line coming from the middle area on the passenger side of the intake plenum, you broke it or left it disconnected would be my first guess.
It supplies vacuum to transfer case switch and cruise vacuum reservoir.
Is there vacuum to one of the ports of your transfer case switch with the engine running?
If not, trace it back to the intake manifold.

 

[dapepper9]

If your driveshaft doesn't spin, vacuum isn't your issue on that end. If the driveshaft isn't spinning in 4x4 you're not transferring any power to it and that issue lies internally in the tcase

 

[dapepper9]

That is, if you mean while you're driving. If it doesn't spin when trying to spin it by hand then forget my previous post

 

[Yeret]

^ Yup. Back when my 4x4 switch took a dump, my driveshaft would spin but there was no power up front due to no vacuum to actuate the CAD. Now, the simple power transfer through the shaft did take the load off the rear a little and I was able to get out of a few dicey spots that way. There is nothing quite like engaging your 4x4 and going into an area that you know you won't be able to traverse in 2wd and realizing far too late that your 4x4 isn't actually working...

If you're lucky, your transfer case linkage just needs to be adjusted. If you're not lucky, get ready to shell out some greenbacks.