I have a 95 Montero SR 3.5, auto. On my transfer case knob I have 2H, 4H, 4HLc and 4LLc. I have a OEM rear locker. Ok, on the dash, the drivetrain layout( 4 wheels, axles, driveshafts and center diff - that lights up) the center diff light is on, steady( not blinking) and has been since I got it. What does that mean? Also, when I try to put it in 2H or 4H (every variation of neutral/drive and forward/reverse) it makes a grinding noise, so I just put it back in 4HLc. Any help would be appreciated!

1995 Montero SR factory air locker,33x12.50x15 At's