97 Z71 Front Diff acuator

I have a 97 Z71 350 with push button 4WD. When I shift into 4 Hi(or lo) I hear it shift but I don't think it locked the front diff in. My friends told me that it was a solenoid or acuator in the front diff that is out. I can't seem to find the exact part I'm looking for. The Chevy house didn't really know what I was talking about either. Can anyone tell me the exact name I'm looking for, or where to find them. Sorry for the long post and thanks.

The actuator on the front is basically the only wire you see that comesout of the transfer case. It is a cylinder looking metal tube with a wire that comes out of the end. It is threaded into the transfer case. The same thing happened to mine. It's about a $50-$75 part.

The sell a mechanical actuator kit that you can buy that is cable operated as the original is a thermal actuator and can fail when it gets wet or take a while to engage at times, the kit is a little more than a replacement actuator but works a hell of a lot better in heat or cold.