I have a 92 4Runner that has a noisy transfer case. It has alittle bit of vibration to it but mostly it just hums. If I move the transfer case lever forward or backward the noise is reduced. If I push the button in and pull it back between 2 and 4 wheel drive it will go away. The noise is the worst above 30 mph. I have tried changing fluids over to synth. Could there be an adjustment somewhere?
This noise or vibration has been there for some time and has not gotten any worse or better.