I recently had my son-in-law change my shocks. Right after that I started to hear a strange sound coming from under the truck/in the engine compartment. It sounded a lot like a couple of plastic shopping bags blowing in the wind, but it wasn't. It was something dependent on the throttle. I only hear it when the engine was under a load, such as going up hill. It usually wasn't heard if I was going under 40 or so, and would quit as soon as you shifted the foot on the gas pedal. I had to get new brakes, and the mechanic found two vacuum hoses off of the front hubs. He put them back on and I thought the sound had gone away. It came back a couple of days later and it is getting louder. I went back to the mechanic and he looked but didn't see anything wrong/vacuum hoses off. I made a recording of the sound but it didn't help him. He suggested I try Ford since it is their truck. They thought it was an air intake sound. I got a new air filter since my old one was a bit dusty, and I wrapped a bag around the air filter drawer because they said it could be the worn out foam isn't sealing anymore. Didn't seem to be it.

I have attached a .wav file of the sound. There is about five seconds of road noise (it is from my phone out the window) and then the "whizzing" starts.

Anyone have any useful suggestions? I plan to tow a travel trailer to Seattle from Montana at the end of the month, and I would like to fix this first!

Thanks!

 

From what you describe it's likely the vacuum hubs engaging under low vacuum. So you my have a leak even though the hoses got hooked back up or something. That is a very common description of what happens when the IWEs partially engage because there isn't enough vacuum to hold the internal springs from trying to engage.
if you want to test this theory make a test drive going up a hill and put it in 4wd first. I'd be willing to guess the sound won't be there.
Search youtube for fordtechmakuloco and iwe or 4wd problems he explains how to test the system very clearly and how to fix it.

 

Thanks! I will give the test drive a shot in the morning. {!-{>

 

I tested it this morning. No sound in 4x4. So I tried it out f 4x4 and then switched in on in the middle of the sound...and it went away.

If this was new I would just change the actuator and solenoid, but I have been driving on it for a while while no one here knew what it was, so I plan to change the IWE's on both sides.

Thanks! I will be happy to have my truck running smooth again!

Curtis in /\/\onTana! {!-{>

 

Thanks for following up that seems to narrow it down alright.
just make sure you have everything working right with the vacuum system with no leaks or it will do the same thing to the new IWEs.

 

That is in the plan! {!-{>