new member question

I have been reading this forum for a while now and any question i had i was able to find the solution to without having to ask. well todays the day. i have a 93 s10 4.3l 4x4 and i have issues with the transfer case. a while ago when it was in 2 wheel and i'd be driving, it would make a noise almost like a ringing. i'd put in in 4wheel and back out and itd be fine. shortly after i replaced  the vaccuum actuator and it hasnt done it since. the 4 wheel light would stay on no matter what mode it was in but it all worked fine. now the light doesnt come on and i think it did the ringing thing again. when i unplug the sensor and put it back in, the light comes on and goes off after about 30 seconds. everything still engages correctly but i'm about to go on a 600 mile trip and i want to make sure. i'm leaving friday at 3 in the morning and will be going the appalachian mountains. i've had my blazer for 2 and a half years and i just love it but lately i'm stressed at it because it wants to have issues constantly. other than my air vents always blowing at least half the air out onto the floor, and my digital guages going out or flickering there is no problem with it. sorry for the long post but i wanted my first one to be well worth it