89 Cherokee 4x4 won't engage

I tried to put my Cherokee into 4x4 Part Time during some crappy weather. The shifter moves as it should, but nothing happens. No noise, no grinding, nothing. From Part Time to Full Time only 2x4 works. I still had to be in Neutral when going into Full Time but no results. Anybody have any thoughts?

Try Jacking up all 4 wheels with jack stands and checking the linkage> iam not sure if yours is vacum activated. If it is check for vacum leaks. Start the Jeep and put in drive and check to see if the diff is engauged in all the 4wd modes. Ive done this with all my 4wd vechiles it helps isolate where the problem is. On your year the diff has a vacum motor on the diff to engauge it check that to make sure it is operating.