I hear a loud banging noise when i put my 99 Tahoe in 4 wheel drive

I had a suburban1999 5.7 when I engaged the 4x4 I heard the sound your describing, it was my transfer case. I never got it fixed and my car got stuck in rear wheel drive, it still worked. What I did to make the sound stop was make sure I was in 4 wheel before driving by pushing the bottom to activate it a few times, even when switching back to 2HI(two wheel) good luck.

It is a sliding drive shaft. This is a problem with the Tahoes and Yukons. It needs a special grease. Ask your dealer...he knows the problem.

Could be ur u joints in the front shaft. Had the same problem with my dodge ram. Check ur front shaft and try to move it. If it doesnt move at all than should be fine. But if it has any kind of play than ur u joints are going out and that could be the culprit.