2003 Chevrolet Tracker no 4x4

My tracker lost its 4wd, sometimes with the wheels turned all the way to the right it tries to engage. The 4x4 light comes on as it normally would, but there are no crunching or grinding sounds coming from the front end. At first there was a clicking coming from the drivers side front wheel when locked in 4x4 and making an abrupt stop on an icy road, now nothing. The front shaft turns, and the 4x4 actuator behind the bumper activates and then stops, leading me to believe that the actuator, and diaphragm in the front end are both functioning properly. Any help would be greatly appreciated, thanks