I have an push button 4 wheel drive in my chevy silverado 1500. I can hear it locking into 4wd in the transfer case, but the wheels wont spin. I put it up on a lift and engaged the 4wd and the wheels then spun, but as soon as weight gets on the tires it doesnt work anymore. I am completly stumped. Just wondering if anyine had any ideas before i spend my next paycheck at a shop. Naythings helps. thanks!
JOE

pushbutton 4wd whats that?

Check the engagement motor at the front diff, it is on the right side

The front axle probably has a vacuum actuated axle disconnect. The lines like to dry up and crack, cause they're often pretty close to the exhaust. Just check your vacuum lines.
Or you might have one of those goofy coil heated expanding gas actuators, I don't know what years had what. I think there's a conversion kit for switching to an electric solenoid. Whatever you've got going on, it's a pretty common problem. The dealer might even be able to help you out with a kit.