Countryboy5612

Any Ideas???????? I have a 2003 Chevy Silverado lS 4.8l 4x4 with a a manual t case lever I can not get my 4 wheel to engage. Checked the fluid in the front diff and don't see any metal flakes or chunks. I put it on a lift and put it in 4h and drive and the front wheels do not spin but I can hear the t case chain and see the drive shaft spinning. When I engage 4h I can hear the actuator on the front diff engage but no tire spin.my indicator lamp on the dash comes on. I'm at a loss the only things I can think are the front diff actuator sounds like it's working but isn't or a total diff failure. But if I manualy spin the wheels I don't hear anything from the front diff. So I figure even though my actuator sounds like it's working it really isn't. Any ideas or conclusions I haven't thought of????