ok well this problem puzzles me. I have a 94 chevy 2500 5.7 aka 350 5 speed. So the girlfriend and I were driving down the free way going 65 or 70 and i hear this humming noise in the front end. First thought check gages they all seemed fine. I look down and my 4x4 light is on but the shifter is in 2 wd i pull off to the side of the road and i hear a bang noise and the humming goes away. From what i could tell my hubs locked in. what puzzles me is why or how they could have if my truck is in 2wd. so i turn off the truck to reset the computer and the light will not go off tried it like 5 times. So i pulled the fuse out light goes off and hubs unlock drives like normal again. My first thought is the hubs but they lock and unlocked so they are working. check my shifter and everything seems to be in the spot it should be. and the shifter is nice and firm no play. So on this model does it have a senser on the shifter or something. I'm stuck please help