4wd won't engage.
 

As it states. 2000 f150 with electronic shift on the fly 4wd. The light on the dash comes on when switched to 4wd. and the solenoid checks out ok. I checked the solenoid closest to the fender and it has power, and has ground when 4wd is engaged. The solenoid holds vacuum when engaged in 4wd and doesn't hold vacuum when in 2wd. It also holds vacuum on both vacuum hoses, so I assume no leaks. But it still won't engage to the tires. No grinding or screeching when engaged/disengaged. Anyone tell me where I need to go form here?

Thanks

In 2 wheel you should have vacuum on the pink hose at actuator and vacuum on blue in 4 wheel drive. If that checks out ok jack up the front end and take the actuator off and slide the lever for the shift fork back and forth and see if your front wheels lock together and unlock. If they don't you have to replace the shift fork. I had to on mine couple years ago. Its basically a fork that slides a coupler over and locks the axles together. Its a common problem from what i heard. Good luck!

+1 on the shift fork. The repair kit is under $200 but you have to open up the front axle to repair it. mine failed when we had 10" of snow, I let the dealer fix it ($800 labor).

exactly how does the shift fork fail?

How does the shift fork fail?

There are two little plastic bushings, one on each end of the shift fork. They wear down and eventually there is not enough plastic to engage the gear in the front axle.

I was told that the rebuild kit had improved bushings that lasted longer, but not sure that is true.

A google search turned up a chap who made bushings out of brass to replace the plastic ones... on the 'other' f150 website. Here is a pic with brass bushings:

http://screencast.com/t/laMRu3pq

'posi-lok' replaces the wiring and vacuum with a mechanical push/pull knob.

Turns out it was the actuator. Thanks for all the help.