My 2007 f-150 xlt 5.4 had been kicking into 4-wheel pretty hard the last month and gradually just quit engaging all the way. I check the solenoid which doesn't seem to be the problem. It went from kick in hard, to almost skipping and now it simply won't engage all the way....almost sounds like a pop can on a bike tire. The sound is coming from the drivers side. I think that it just needs a new wheel end but I'm just starting to get interested in vehicles so I'm not the guy to be diagnosing this. It's got around 86000 miles on it if that helps.

It's going to the garage on Monday I just want to make sure they don't take me for a ride.

 

What do you mean by kick in hard? Are you talking about the wheel hubs engaging or the "klunk" from the transfer case? You could start with the basics, i.e. putting the front end up on stands, starting the truck, and, in 2wd, seeing if the front wheels (when spun by hand) also spin the axles. If they do, you can start testing vacuum lines to see if they hold and you can replace the IWE hubs (they're pretty cheap).

 

To me it sounds like the hub. It has splines on the back of it that meet with the IWE actuator which also has splines on it. If they shear off then it will not work. You can check this just like the post before this one said. It should be a fairly easy fix but you never know. Goodluck!!!