Have a trusty 05 stx 4.6 4x4 automatic 44,000 orig. miles/owner ext cab pick up.Just lately I thought I picked up at tree branch or someting make a noise very similiar to pulling a hung up branch or sumting..Stopped,looked under truck (everywhere) no dice!
Then did some reseach..noise went away when not giving it gas or gliding in nuetral just when light or heavy eccerating! Any body up on this one??
Where do I begin?? Thanks! Great Forum!!

 

Check your heat shield around your front driveshaft, thats what it was for me.

 

Thanks but been told its something about the IWE actator or vacum leaks that engage and disengage front wheel drive..

 

Here's a few link to read up on the IWE and related 4x4 issues. Usually easy to sort out and repair.

https://www.ford-trucks.com/forums/1211749-4wd-not-working-help-me-pinpoint-my-issue-plz.html#post12662529

http://www.f150forum.com/f72/how-diagnose-your-4x4-system-esof-186872/

https://www.ford-trucks.com/forums/836438-everything-you-wanted-to-know-about-the-iwe-system-and-then-some.html

 

Thanks..Good info!

 

You're very welcome. My great uncle was a China/Guadalcanal Marine. Retired Army myself. Thank you for serving.

 

Just chased this down _ FINALY _ on my son-in-laws truck. The IWE write up referenced is one of the best there is, and I did find a check valve leaking when checked with a vacuum gauge - BUT… his was not the IWE. It was a bad bearing assembly.
We chased that damn scratching sound for weeks until it became a grinding sound and were getting nowhere. I kept checking the pieces of the IWE system. The wheel ends both checked OK and would hold vacuum. I became convinced it had to be the solenoid intermittently working and not working, but after replacing it – still noise!
Frustrated, I lifted the entire front and put it on stands – then spun the wheels with engine running and without to see if I could hear it with my ear right at the wheels with the CV shaft spinning and without. That’s when I noticed the passenger side wheel had a little wobble – looking from the front. The driver’s side was true and straight.
I pulled the wheel, caliper, rotor and bearing assembly. The bearings were shot and sloppy.
$180 to Napa and his truck is back to its old self! Awesome.

 

Left front IWE end (actuatorr?)replaced $146 parts and $143 labor at local shop..hope this is the end of it..