4 wheel drive will not engage on 1999 Chevrolet Suburban 1500

when selecting 4x4 push the button and hear a clunking noise

Asked by for the 1999 Chevrolet Suburban 1500
2 answers
CAN YOU GIVE SOME MORE INFO PLEASE.SOUNDS LIKE ACTUATOR IS NOT WORKING CORRECTLY
Well how about some more info!! Light on switch flashing??? Get it fixed already?? Nothing wrong anyway??? You'er supposed to hear a clunking noise when the transfer case shifts!!!