I have a 2004 F150 Lariat and my 4x4 seems to not be engaging. I read through the 4x4 diagnosis and we performed a bunch of tests on the vacuum system. First of all, there IS vacuum at the wheel, when we turned 4x4 on the vacuum stopped, and we tried spinning the wheel and seeing if the shaft spun with it. It didn't spin with it. We tried simply disconnecting the vacuum line altogether and it also didn't engage the hub with the axle. My question is this: where do we go from here? Do we take apart the actual hub and simply look at the IWE for damage? What would the damage look like? Is there a tutorial for disassembling the hub? Or what else should we do?

 

Replace the hub.

 

Before you replace anything, make sure you check the system correctly. To do that you need to have the truck raised up and running. This is the only way you can make sure you have vacuum at the wheel ends. Once properly supported and running with truck placed in 4X4 you should have vacuum at the wheel ends. With the truck off, even when in 4X4, the IWE will disengage. That is the proper operation. With it running, if you have vacuum, the wheel ends should lock.


http://www.f150online.com/forums/art...then-some.html

 

might as well replace both sides while you are at it. not too difficult. took me less than an hour per side, including rebleeding the brakes on one side due to taking a line off on accident.