I just rebuilt my whole vacuum 4x4 system, I can prolly help, what do you need specifically?

 

Red hose is the Vacuum supply to the T/C swich.
Green has vacuum in 4x2 only
Yellow has vacuum in 4x4 only
Once the axle vacuum motor has COMPLETED its travel, it then supplys vacuum to the white hose and the electric switch near the blower motor completing the circuit to the 4x4 light on instrument panel.
Blue hose is just a vent

 

Thanks that is what I needed maybe now I can make some progress.I just bought this Cherokee a few weeks ago "$500" I have no rear end, It just grinds. At least a bad ring and pinion, and the front wont engage, I can atleast work on the cheaper things until I get to the rear, Thanks again..

 

those hoses are supposed to have colors???

mine are all black, haha

also there is the switch on teh back of the t-case.

I had a similar problem, my front axle wouldnt engage, the guy who owned it before me installed the vacuum harness to the vacuum disconnect backward so the whole time it was engaged except for when I turned on the 4x4, then it disengaged. unfortunately being engaged all the time caused the diaphragm to rupture. good luck with your jeep

 

Ed, I MAY have the green and yellow backwards. But you get the idea. A mityvac setup ($30 at local parts0 was indispensable, but my 300K mile 87 Chief had a bad(stuck) T/C switch, a functional but leaking vac motor on the front end, and all the plastic hoses were broken, even after replacing all that, it STILL didnt work! Thats when I was able to pull a vacuum on the steel lines when they were not hooked up, they were plugged! Then it started working.

 

Since i Had a new vacuum harness, it would only hook up to the vacuum motor one way. You can still get them through dealers, under Vintage parts.