When I push the button for four wheel drive the button lights up but the front wheels do not engage. I replaced the front axle actuator and still nothing. I can hear the shift motor on the transfer case working and the front axle actuator working as well. No service four wheel drive is indicated on the dash. When I push the four low button the transmission is geared down but still no power to the front wheels. The transfer case even makes a clunking noise when shifted to four low as if it is working. I'm lost. Any suggestions on what to do?