I got about 2 months left on the warranty and I'm going to get to the bottom of this problem this week...i've done a ton of research on forums for the last 2 years about this problem and the best thing I've heard is that it could be the alternator or pressure valves...I'm going more towards the pressure valves cause it makes more sense and it is indeed a whistling noise like a high pressure whistle...Mine 06 4.6 stx 2wd only does it when its cold and will do it every morning when its starting up and also when its going about 30 or 55 to 60...i dont have a rpm gauge but it has to be something to do with rpm's or something...it does it when it starts up too soooo idk what the rpms are there...idk...anyone have any answers yet?
I have this annoying whistling sound too! To me it sounds as if something is spinning, almost like a scraping noise. gets higher pitch when rpms go up. I've been to my local shop and they had no idea what it is, they said possibly tranny. I went to the transmission shop and we test drove it and he said its not the tranny, because you literally can't feel it at all.
It is a definitely a weird noise and turning the radio up is my solution but i would like to know what it is!
6" Zone Lift, Toyo MT, XD Addict, Zone Nitro Shocks, K&N CAI, Flowmaster American Thunder, Gryphon
Cold Start Fead Hoot-Whistle Noise-built before 1/c
Pub. Date Feb 7, 2008
5.4 and 4.6 engines built before 1/28/08 may exhibit a front related high pitched metallic whilstle/hoot noise after a cold soak 4.4 C. Noise may be caused by the grooved nylon FEAD idler pulley.
Service procedure to correct. Replace the nylon FEAD idler pulley 6L3Z-6C348-A Idler Pully.
Same issue. 2006 SCREW 4x4 - Only happens when temp is down in the freezing range.
Originally Posted by nashtruck
I have had the same problem for four winters now and it is definatley not the alternater. Its a whistle, not a squeal. It only happens sometimes in cold weather. It did happen this morning but after driving a few blocks it stopped. Tried having the dealer look at it under warranty but of course...no whistle that day! I would love an answer to this.
I had that same Thing the temperature would go below freezing and i would here a loud whistle except my problem was the alternator I got a new alternator and it's never done it since all these trucks do it i guess it's the bearings
Same problem on my 08 Xlt 2wd with 30,000 on a 4.6. It only happens between 1200 and 1800 rpms. Sounds like a bad turbo spool or air being forced in through a small opening. It goes away after 1900 rpms and when I'm off the throttle.