I have a 2003 s10 Zr2 and as a lot of you know it has the push button 4wd system. I bought it with the transmission needing a rebuild, and before I even got the trans put in I replaced the switch on the transfer case. When I first got it running, 4wd only worked when it wanted to but I didn’t really care as I just got it running. But over time I got tired of it and run new vacuum lines and put a new check valve in with a new cable for the front diff. The actuator is fine and I know it’s getting good vacuum to the t case so I’m just wondering what else is there to check because I’m completely lost at this point. Maybe a bad switch on the transfer case? It was a doorman replacement so it may be faulty. Any and all help is greatly appreciated!! God bless.