1990 Jeep Cherokee Sport, 4wd does not engage with shift lever - no dash indication, transfer case is moving (went into 4 lo, could tell by rpm) but the front isn't locking

 

I'm wondering if there is a relay that engages the front end? I can see three relays and one large resettable breaker near the fuse box, but of course they aren't labeled

 

have no manual, doing web search

not sure about what years had this but some of them have a front axle dissconnect. it uses a vacuum motor on the front axle that moves a shift fork and connects the axles shaft. the right side axle shaft is a 2 piece shaft. check and see if you have this. it bolts to the right side of the axle and has vac lines running to it. iirc it also has somthing to do with the 4wd light turing on also. somtimes it is as simple as a bad or loose vac hose

cool, thanks, i'm on it in the a.m. to see what can be seen

I don't have any experience with a jeep but my blazer had the same problem and it was a combination of bad vacuum switch on the transfer case and the vacuum actuator that engages the front axle.

This was a freebie. Wish it was always this easy... I was underneath today, and I followed the vacuum lines to the front axle - the lines were not actually connected but laying 1/4" back from the vacuum module. The rubber block that holds the hose cluster had pulled off.

 

I cleaned the dirt from the ports, plugged it back in and safety wired it in place. Guess what? It has 4wd again, that's all it was.

 

Wish everything was that easy.