01 Sierra Front diff not engaing

[knucklehead27]

I have an 01 sierra z71 slt. I'm at ends with a 4wd issue. The push button system seems to work fine. I hear the TC engaging and I feel the 4lo gearing but theres no power to the front. I replaced the front diff actuator and I hear it when switching to 4x4 but again, no power to front. What else could it be? TC not fully engaging? Problem in the front diff? any help is much appreciated