I had an elbow coming off the wire loom on the firewall that was pointing forward on the intake side of the motor. My heat selector stopped working, so I knew there was a vacuum issue. The elbow had nothing in it and had a vacuum leak as a result. I shoved a stick in the elbow to close the vacuum leak. But does anyone know what that fitting went to?

What things run off of the vacuum system?

 

4X4 and Cruise Control as also controlled by Vacuum

 

I've got 4x4 shift on the floor, so do I still have vacuum there? No A/C. So my only vacuum use is for the selector for defrost, floor, etc?

 

i just had this problem you will not have cruise. if you have a jake break it will not work and your 4x4 acuators will not work. you can shift the t-case but the axel will not lock. i fixed mine by finding the cracked leaky hose above my engine next to my break master cylinder... i put new hose on and it was fixed. you can follow all the line very easily.
you will start derectly under your injector pump and find the plastic tube that goes to your wiring lum and just follow it untill you find a cracked hose.

 

NOTE - some of the 4x4's have a "CAD Disconnect" (IIRC - Common or Central Axle Disconnect) is a vacuum operated system. It is on the older 12V Cummins 4x4 and the 24 Valve Cummins - but not on 2002 Dodge/Cummins. The CAD "hardware" is between the front differential and the passenger side wheel. (My son's 1997 has the CAD hardware, my 2002 4x4 doesn't have the hardware.)

 

02 is the only year of the older body styles to not utilize the CAD, 03 and newer trucks use AAM axles and not Danas, which are also CAD free. But the four wheeel drive hoses can be a if they become unplugged when ur in the mud and can't get ender the truck to reconnect them.

 

What about 2001.5? My 4x4 light is not working either. Figured it was related to recent transmission removal to change the torque converter.

 

Could be the wiring for the sensor in the front axle. My buddies old truck had that happen. The truck would go in 4x4, he just didn't have any notification of it.

 

If I have CAD, where is it located and what's it look like? 2001.5 2500.

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Answering my own question. I did a search and got some good info on the CAD system. Although mine appears to be electric rather the vacuum operated.

After transmission work the 4x4 light is not coming on. Makes me wonder if the CAD is working also. Is it ok to use low range if the front axle is not being actuated? Going huntin this weekend. Anyone know what fuse is involved?

 

I know i've been all oveer the board on this thread.

CAD is vacuum, I assumed that the red and black leads were electrical. Transmission guy found the disconnected vacuum line from the transfer case to the firewall. 4x4 and light on dash now works good.

So it looks like the vacuum runs the CAD, Heat/defrost selector. No air conditioning or cruise.

Thanks!