Good deal! And from one Irishman to another thanks!

 

Definitely sounds like a leak but in the 4wd system because the engine will lose vacuum as you increase RPM so the symptoms sound opposite of an engine vacuum leak. Since the changing of the 4wd system makes it change, it's in the lines to the actuators somewhere I suppose. Could be one of the valves along the way from top to wheels.

Since it's opposite, when the truck is idling it (the 4wd system) has the vacuum it needs to function but as you increase RPM, vacuum drops and a secondary source (or some sort of regulation of the vacuum it has) comes into play. This would be where I would start looking.

 

It ended up being the check valve between the throttle body and the solenoid, as well as the vacuum line that exits the solenoid. Since the hissing sounded like it was coming directly from the wheel, I have to assume that it was indeed my IWE's trying to engage. It definitely was not a metal-on-metal sound, like everyone else describes it. But, it makes sense that even with the bad valve and vacuum line, there was still enough vacuum to keep the IWE's out of the hubs until I gave it enough gas, reducing vacuum below spring pressure.

 

What part if Ireland are you from? I'm from Kilbarrack about 5 miles from Dublin city center.

 

I should clarify. I'm Irish/American but proud of my heritage.

I would love to visit some day and trace my roots. A tree was done years ago but not too extensive. (Note to self, do a NEW family tree. ) My Great Grandfather is from there and came here with his family when my Grandfather was young. I'm a second generation Irish/American, my Father being the first.

 

I'm Irish/American also. Grew up for 7 years in Norfolk Virginia. Then parents split up and my mother took us back to Ireland and then i moved to Canada in 1989 when i was 24 where i live today.

 

Cool! Yeah, one day we will make the trip. I am really interested in exactly WHERE my family is from.

 

I replaced the hubs, IWE actuators and solenoid for my 06 F150 and still have the same grinding noise in 2wd. I tested the vaccuum pressure after replacing the solenoid a few months ago and had 18" at the wheel ends. The hubs and actuators were already toasted....The new hubs and actuators work great now if I keep them in 4wd. I'm assuming I have a leak somewhere and need to check the pressure again. I think there are a few check valves in the system.. I had strong vaccuum presure today at the solenoid but weak at the IWE's (I believe it only needs 8" to keep the hubs open/ 2wd).

I'm am really starting to regret buying a F150, after dealing with all of the problems... fuel injection going out at 39K and the 4wd system imploding a few moths later I'm not impressed. The dealer is aboslutely clueless and if it wasn't for this website I would have probably hydrolocked my engine when two injectors stuck wide open (covered by the EPA emmissions law in CA). I have spent approximately $700.00 so far on parts for the 4wd (tasca Ford in RI has the best prices I found) and 2 hours time to swap them out, actually a pretty simple job after reading the posts w pics here.

Any help or suggestions on the vaccum system would be greatly appreciated!!!!

 

TN-F150, you are the man! Like you said there is no help out there for this problem and your post really shed some light on it for me. I am fixing mine soon thanks to your info. Thank You!

 

somewhere back in this thread I already posted this...

http://www.ford-trucks.com/forums/83...then-some.html

For trouble shooting the vacuum system, etc.

 

Glad it helped!

 

BTW, I got you message and it's pretty much all here. The first page has the PDF's of the Ford documents and the rest is pretty much spelled out right here.

Good luck with it

 

Ok question does the actuator engage the hub to the cv axel? or the other way around?
My problem, when i put it in 4wd HI and give it gas theres a loud grinding noise from the front left wheel, which i assume is the IWE but i wonder if its the going to be as easy as replacing just the actuator or if i need to replace the hub and or the cv axel?

 

The actuator and the IWE are the same part. IWE is just an acronym for Integrated Wheel End which is an actuator. The actuator slides a gear out and make the axle (CV joint) and hub gears, one gear to make the front wheels engage in 4HI/4LO. The hub and axle (CV joint) gears are made of hardened steel while the actuator gear is made of a softer metal that takes the brunt of the damage. I doubt you will need to replace anything but the actuator. Don't forget to make sure you replace the solenoid on the firewall with the latest revision, and make sure there is no water in the vacuum lines.

I really need to make a cut away view of this assembly.

 

That thread was 2 months after mine and wasn't around at the time I needed it, hence why I did this write up.

I didn't dig through that thread to see what you are referring to posting about so I'm not sure exactly what you mean...

But thanks for contributing.