Whistling and Clicking on '04 Expedition

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AstroGeek

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I currently have 2 different issues on my '04 Expedition with the 5.4 engine.

The first is during colder weather, or even a cool morning, when I first crank it up, I get a loud high pitched whistling sound. My initial thought is this is a vacuum leak somewhere. I've previously replaced one of the vacuum hoses back by the firewall and this went away for a while. But it came back about 6 months later. It's probably worth noting that once the engine has run for a bit, this whistling sound does go away and I typically don't hear it during the summer months. I've looked over all of the hoses I can see, and have run my hand over the others and don't see or feel any that seem like they have any holes.

The second, and more concerning one, started not too long ago. When the engine is under load, like going up a hill (we have plenty of those here in CO), it's making a sound that I can only describe as a weed eater hitting sheet metal. As soon as I hear it, if I take my foot off the gas, it'll go away. It won't come back immediately. But if I'm going up a hill at the time, after 5-10s I'll start to hear it again.

I'm thinking it may be exhaust related, especially since it's not directly related to acceleration, transmission gearing (does it with and without O/D). I'm just not sure where I should looking for this one.

Any thoughts or advice on either of these would be great!
 
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sjwelds

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The second issue I would guess to be the iwe system. Try putting it in 4A/4H and see if it does it.
Basically a vacuum controlled device that locks the hubs when you engage 4WD. So it could be related to the first problem as well.
 
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AstroGeek

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After putting it in 4A and going for a drive in areas where I've heard it before, I can't get it to do it now.

It was a little warm this morning, so I didn't hear the whistling.

For the IWE, is it the solenoid that I should look at replacing to fix this? And where would I be able to find these little buggers?

Anything else while I'm at it?
 
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