Hard to get into 4wd and kicks out
 

My 1972 k10 seems to be getting harder and harder to get into 4wd. When I put the transfer case into 4wd and start to move, I hear a grinding type of noise when it should be engaged but isn't. It also kicks out of 4wd occasionally. I have a NP205. Any ideas?????????

Bad actuator would be my guess (I had similar symptoms a few years ago on mine and thats what it ended up being). I think a new one would probably run you about $50 or so. . .

While you're down there, check the gear oil level - in my experience they have a nasty habit of slowly losing oil due to seepage over a long time - might be a related problem or at the very least some good preventive maintenance.