150 4WD

2003 Ford F-150 • V8 4WD Automatic • 84,000 miles

I have a ford f150 and the 4wd does not engage. When I turn it on it sounds like it is trying to go into 4wd but nothing happens. Any ideas? Thank you.
January 22, 2011.

Check the actuator for operation. It may be getting stuck at one point.