Well, I have had the high-pitched whistle for a while with mine and posted about it earlier. Mine is clearly a leak somewhere, and it is only present at certain throttle positions, which I can't duplicate while the truck is sitting. I have the same whistle with the stock air cleaner, the 3" AF-1, and the 3.5" AF-1. I'm sure the engine is sucking air somewhere. I've checked fittings everywhere, and can find nothing. I'm betting I have a gasket or something allowing the engine to suck air. I dont know what the chrome rails are on top of the engine, but notice that at the base of each where they enter the manifold, there is dust-covered oil around the base - clearly a leak.

I listened to this with my service guy, and the whistle is really noticeable through the AF-1 intake filter. The service manager thought it was AF-1 related. It's not - I've tried the stock and both AF-1's and it's present with all intakes. I'm thinking it has to be something with the throttle body. This weekend I'm gonna try to check all the bolts, nuts, and washers around the intake manifold.

I know I trade yearly, but if I have to listen to this whistle until spring, I'm going to pull th engine out and put in a Powerstroke!

Have any of you tried a new throttle body or one of those POS tornado spacers? It seems to me (08 single cab 5.4) that when I put my K & N on, thats when I heard the whistle and its only at cruising speed.

It has to be throttle body related. Maybe one of those spacers will help the airflow into the TB? Maybe I need to just get an aftermarket TB?

I actually put the stock intake back on a couple of weeks ago, and the whistle went away. Kind of weird because when I tried this a month or tow ago, the whistle was still there with the stock intake. I am convinced the design of the stock intake muffles the sound, and the large bore hollow tube design of the AF1 compounds the whistle and magnifies it substantially.

I still can't figure out why after 10,000-15,000 miles the whistle suddenly developed. The truck was quiet as can be for the first 15,000 miles, and now, its been whistling for the last 15,000 as I approach 30,000.

All that said, I just can't stand the throttle lag and torque converter unlocking with the slightest touch of the pedal with the stock intake and stock tunes. I cleaned my AF1 filter last night and will re-oil it tonight. This weekend, I will be reinstalling the AF1 (3.5") and my Troyer 93 octane tunes. I think I'll just have to get used to the whistle because stock driving just 'aint for me.

Well guys, after just over 40,000 miles and two years of listening to this annoying sound whenever it was cold - and being told by my dealer that it was a known problem (with no known cure) it's fixed. I replaced my alternator 30 minutes ago with a $189.00 Ford remanufactured unit. I was pretty sure we hit it right when I spun the pulley on the old alternator and it squeaked. I just drove it home from the shop in 23 degree weather and the silence was golden. Hope this helps some of you other guys (and girls)!

You guys are fraking anal.... Sheesh. Mine does this every winter. Its cold here A LOT :coffee: I just deal with it and adjust the throttle position so it reduces the whistle.

What I really hate is the drop in mpg in winter. I seem to lose 2 mpg every winter. and it bounces back in the spring. Luckily gas is cheap right now. :thumbsup:

Smokewagun: you trade every year? Shoot your truck looks great. let us know when you trade - maybe I'll upgrade :beers:

Took my truck in to have it looked at because I only have 10,000 and it was doing the whistle at low speeds. My guy found water in the front diff. He changed it and the problem went away. Maybe something to try.

I suppose one could call me anal, but consider this. My whistle was so loud that at 62 MPH on the expressway in traffic with his windows rolled up, the guy next to me got startled the other day. Then of course there was my 1,600 mile round trip to North Carolina last month where it whistled most of the way down and back. Am I anal or did I almost go postal? To tell you the truth, it was bad enough for me to consider selling the truck.

I would not have made that trip without driving off the road into something sharp. That's nuts, i hope mine does not do that when I get more miles on it. Mine was just doing it when it was cold and stopped above 10 miles an hour or so. I really hope they fixed that problem with the 08.

So alternator could be the problem?
I had a 2008 Loner XLT that did that same thing. Never mentioned it to ford, but just this year, my truck started doing it, and im a little concerned.

If you go way back to the beginning of this thread, you'll see a fairly complete decription of the problem / symptoms posted in by me. My whistle started when the truck was still under warranty - which kind of ticks me off now. There were folks pretty early on who said it was the alternator, but my dealer insisted it was not - and there was no cure. They said it was "intake related" and from the symptoms I had, I could believe it. I didn't want to drop $189.00 on a non-returnable part that wasn't sure to solve my problem either. But in the last month or so, it really started driving me nuts, so in the alternator went. Somebody saved a couple of pennies on the bearings in that bad boy from the sounds of it now that it's out. Silence is truly golden!
:thumbsup:

Dayum. Mine only does it intermittently for 10 - 15 minutes... Constantly would suck. Scaring other drivers = priceless. That's almost worth not fixing it.

i just realized this but 2stroked you are absoutely right about the alternator. i have had this problem the last 2 winters. my alternator went a couple of weeks ago and now that i think about it i have not heard that damn squeal since.

Noticed this on mine this morning when it was 29 degrees and the defroster was on, although not bad enough for me to have a new alternator w/2k miles swapped out for a rebuilt one, I can live with this for now. If it get worse, then it will go to the dealership. I try to avoid them like the plague if at all possible, while their not all bad it seems more times than most, the ones I use do more harm than good. Maybe its my area of the country, dunno. YMMV

My wife's truck is making this weirdniose only during cold temps also. Took it to dealer who replaced throttle body. Noise still there. Replaced belt. Still there. They they said it was the K&N air filter. Just bought new Motorcraft filter and installed. Still does it!. I started the truck with the remote start and had my head under the hood. Truck ran about 30-45 seconds and started making this jet engine sound. Drove to dealer and it did it twice during the trip (about 9 miles). Dealer said it is air related. Stated they took the belt off and drove it and it made the noise. Everything is stock on this truck. I'm baffled.

Can I quote myself? :lol: I reinstalled my tunes and the AF-1. Guess what? The whistle/squeak is back. It is definitely intake/throttle related. I am thinking about getting am O-ring to put around the MAS to seal it better and then seeing if it helps. I may try the old brake cleaner deal by spraying it around the intake fittings and throttle body to see if a change in engine RPM (surge) indicates a leak somewhere. I was accepting the alternator thing until the stock intake eliminated the noise. I'm sure the AF-1 is just magnifying the noise... why would the AF-1 start this noise after thousands of miles? I'll tell 'ya, sometimes it's so loud, the guy in the car next to me gives me weird looks. I hate that. I think I'm driving a weenie whistle! :lol: