Someone posted a reply to the service 4WD light coming on in the silverado. Said he replaced the push button assembly and afterwards tore the old one apart and said he could have re-soldered the contacts. I have been having the same issue with my Z71 and thought I would give this a try. It took me about 20 minutes last night to take the button assembly out and resolder the pins on the circuit board. For the first time in 3+ years, I can now just lightly press the button and 4WD engages and disengages perfectly. Just wanted to thank the guy who suggested this.
Brian