4x4 not working help
 

So I have a 1991 s10 blazer 4x4 4.3l I haven't had it in 4wd much..only a couple short times...usually I can see mud sling or dirt in 4h but not to much compared to the rear..and I used to hear a wine in 4L ok so that was normal..the light taking a few min to kick on at the shifter idk..but I was at a friends place 2 weeks ago and it was down poring we were fixing his blazer same as mine..he has bald tires so couldn't move out of garage so I backed up and sank so I put it in 4 to help to not make roughts all so well and good but when I put it in park it sounded like grinding gears so I slammed it back in drive and still did it so I killed it put it into 2wd and everything was fine tryed 4 again no issues.. But I noticed when I pull lever you can hear gears grab and feel it..neutral 4l and drive or neutral for 4h..now my buddy's goes into 4h smooth almost like there is no gears at all but does the same in 4l as mine but his fronts never moved...now back to my point I was at beach today and got pulled out of mud pit and sand..my 4 anything doesn't seem to we engaging and light didn't come on earher...help