1994 Chevy Silverado 4WD problems

It does not sound to be a push button 4 wheel. When you have the truck in nuetral and are using the column in the middle by your feet make sure when you put it in and out of 4 wheel you do 1 continuous motion. If you stop in each gear (4h 4l 2h nuetral) it will grind. As long as its a swift constant change of the gears it shouldnt grind at all. As far as the ac making noise when you start, is it a squeeling noise? Can you try to describe it more? Sounds like maybe it could be pulling the belt over the pulley maybe or a short cycling through the compressor.

No my 4wd is on the floor and ya I stop my truck and put it in N to shift it and when I go up on the 4wd to 4h I think that is what is on the very top when I put it back in 2h it makes the grinding nosie and idk y my 4wd dont lock up at all and my nosie is comeing from under my glove box and its like a thumping sound

The thumping sounds like a bad actuator its a cheap part and easy to replace it controls a door and sounds like its bad what you hear sounds like a thumping if you put your hand under there and hold the plastic door in place you will probably feel the thump. Thats for your ac it should probably happen as soon as you start the vehicle and turn the ac on last anywhere up to 30-45 seconds. It is a little black plastic housing looks like a square with a loop hole in 1 end. Replace that and your thump will go away. As far as the 4 wheel. Has the grinding happened since you owned it or is it a new developement. I only ask because mine would do it to me also if I didnt change from whatever 4 wheel gear I was in back to 2h in 1 motion.

No I just bought the truck like last month and I tried to see if the 4wd work and it didnt I can put it into gear just fine but when I go the tires or nothing locks up it stays in 2wd still so idk what the problrms is people r telling me its a sensor and idk how to check the fulid in them or nothing