No 4wd lights coming on!

I have a 1991 Cherokee Sport 4.0 auto that "feels" like it is shifting into 4 lo, but apparently last time I was stuck, only the right rear was spinning (mud!), and none of my 4wd lights were on. I know there's some vacuum operated stuff on the front diff, but I don't even know where to start. Any ideas?

Pull the two vacuum lines off the actuator and test for vacuum. You can just put your thumb over the hole and feel it if you don't have a gauge. One line has vacuum in 2WD, the other line has vacuum in 4WD. Put it in park in 2WD and check for vacuum, then do the same for 4WD. If there's no vacuum in 4WD in one of the lines, work your way back to the t-case vacuum switch (on the rear of t-case next to the rear output housing, looks like a hex thing with 4 prongs coming off of it). Replace any leaking vacuum lines (I've used rubber vacuum line in place of any steel lines with success) and be sure to zip tie/clamp/whatever the lines out of the way of anything sharp/hot. Make sure you leave enough slack down towards the axle for suspension travel.

If you have vacuum in both lines, check for a vacuum leak on the actuator. Plug only the line that has vacuum in 4WD back into the actuator on the axle. Shift to 4WD and measure for any vacuum leaked to the other input on the actuator. If there is vacuum being leaked across, replace the actuator.

If you have vacuum to the actuator, and the actuator isn't leaking, pop it off and check the shift fork/collar for damage. The D30 CAD uses an aluminum shift fork which is very fragile (I broke 3 of them when I had a CAD D30). You can grab a cast iron one out of a Dodge D44 CAD setup and it slips right in. I grabbed mine from an '87 Dodge D44 CAD setup, not sure if the newer ones work or not (94+) but I would imagine so.

Those are really the only issues I've had with the CAD setup in both my old D30 in my first XJ and the D60 in my '01 Ram (identical setups). They're pretty reliable systems with some minor maintenance.

You can also go the posi-lok route if you want to eliminate the vacuum setup. This also gives you the ability to shift into 2-LO (shift t-case to 4LO and don't engage the cable shifter...basically your situation right now ).

Thanks bud! I also read that you can slide the collar over to locked position on the front diff...good idea?