I haven't seen an answer specific other than an oblique mention to my question. When transfer case is in 2 wheel drive, jeep off, should the front driveshaft spin freely? I have had many sneaking suspicions that my front diff isn't engaging, even though the transfer case puts it into low gear.
as an example, a couple days ago I got stuck, one tire on rear no traction (love open diff!) but no tires up front spinning or moving. I assumed initially that the tire I couldn't see was spinning but after I got pulled out there was no evidence of it spinning at all. Could I have a bad front end?
Additional info:
front end lobe-grinds on steep downhill stopping and hard stopping.
Red vacuum line (traced to transfer case) not connected and not sure where it goes. It has no fitting on it.
Vacuum disconnect vacuum line connection will not remain in place, and entire vacuum disconnect assembly rotates freely.
Blue vacuum line is not connected to anything in engine bay, but has black nipple connection on it.
Red green blue yellow vacuum lines go from connecting harness at transfer case to engine bay. The yellow is mated with a white cable (appears factory) and the white goes to a T. One side of T goes to vacuum disco (joining green yellow at the connection on axle) and the other side goes to a blue fitting with two wires (hot and ground assumption). Blue fitting has no other connections.
Hope this (rather lengthy) explanation helps someone to help me out. Places to look? Ways to tell if my front end is working? Thanks

 

The vacuum actuator is a common failure point, one of the lines could be leaking or the diaphragm itself could be bad. Jeep did away with the vacuum disconnect on the XJ in 91. You can pull the CAD actuator off and permanently lock it like the 91 and newer ones are.

 

Good links found with CAD bypass search... Much better than how I was searching. Question. Can I just remove all those vacuum lines if I use the stacked washer method?I'm working on taking out all equipment that is non-essential, and this seems to be one of those things.
​​​​Could CAD issues be causing the front end lobe grinding?
Could CAD issues cause the front driveshaft appear completely disconnected?
Essentially I think all other questions have been answered, thanks!

 

Yes, all the lines can be removed. Just plug the one on the firewall that feed vacuum to the system.

Here's a link on eliminating that system in about 20 minutes.

https://www.cherokeeforum.com/f51/fr...ss-91-a-38629/

 

I like having mine working fine as designed.

 

Yeah. we've been down that road before

 

Well it turns out that the vacuum system in my Jeep is completely .... Err modified? In a nutshell, there is no vacuum in line at all for the vacuum disconnect. Therefore, what IS there is vestigial at best. Completely unfunctional. Also, did FURTHER digging. The line that should go to the bi-metal temp sensor instead goes to the heater control valve (you should see what this does to my blend gate when the air control switch is turned to the "off" position! Give it gas, have vacuum, blend gate closes. At little engine load, no vacuum present, blend gate opens... I gotta get a video and share link!). The line that should go to the egr has a screw in it. The remaining from that three way vacuum connection goes to the vacuum controller. On the cannisters side, the one that should go to the air box just... Ends. Not capped, just... Ends. The other line from the canister goes comfortably to the gas tank. What is it's purpose? It is not drawing any vacuum either.
i think the P.O. was dead set against vacuum lines. Got rid of all he could.

 

I bet they eliminated the vacuum storage canister also. This is an easy fix.

 

nope it's there... But then there is this....
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SirCyber,
cruiser's referring to the vacuum canister where as your referencing to the evac canister.
Vacuum canister is an elongated "plastic" part with one line attached. Should be on the right side behind and attached to the front bumper.

 

Some pics, including relevent pics to my original post These are the top end vac lines for CAD. Note red and blue unconnected. I believe one is supply, and other may be return?

Cut and sealed with a screw. Should go to egr
Egr bypassed. I was really worried about this initially but a. Jeep runs fine and b. read up and it's fairly common See the small tube under the windshield washer reservoir? That comes from canister to the bi-metal thermal sensor. Which I don't have. This is an overhead of the sweet bypass! My finger is at the fitting that connects to the pressure regulator (covered by my hand). Pointing to the new heater vacuum feeder line routed across, well, everything. The hose my finger is on is the other side of that feeder hose. Note the pinkish and black vac lines to the left of my finger? Those come into the cab. The pink one goes to the heater control valve on the heater supply coolant loop.

 

ahhh see... Yes they did indeed completely delete that one

 

You know you need one ,right?

 

Purpose? The canister appears to just be a reservoir. Just noticed that the MAP sensor only has one input of two installed, and one of two inputs for the intake manifold. Based on the drawing provided by cruiser, the canister (eventually) ends up at one side of the intake manifold. The diagram does not show what goes to the other side of the MAP sensor, if indeed anything does.
What harm may be happening here since it's not connected correctly? The jeep runs great, never stalling, no stuttering. Slow start, but that's common and easily fixed. No excess fumes, good power... In short I have zero indications of faulty or failing operation.

 

Purpose?
The amount of vacuum varies with the engine rpm's. Without the reservoir any vacuum assisted features on the vehicle can be affected by the varying amount of vacuum. Especially when it's low. The reservoir prevents this by keeping the amount of vacuum where it's intended to be for proper feature function.