Had this on an older F150 FX4. It’s was the vacuum reservoir releasing. Dirt, dust, moisture, etc can cause the actuator to not open/close efficiently. It’s gives that odd whistle when power is removed. This can cause the shift on the fly hubs to fail if the crud gets through the vacuum lines or the huns only partially engage. You can diagnose this with a vacuum gauge.
Anyone figure out the high pitch whistle sound when shutoff?
- Thread starter Badgertits
- Start date
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Badgertits
FRF Addict
Good idea but I don’t think so. #1 def isolated somewhere deep in the engine Bay Area & I hear it when underneath the oil pan area when laid out on a creeper trying to figure out. Also- does it regardless if I was or wasn’t in 4wd or even if 4wd hasnt been used in a long time.
Also- wouldn’t I get some grinding noise or the truck may stay in 4wd etc? I may swap out the IWE check valve w/ new designed part anyhow as it’s a $10 part- but I don’t think that has anything to do w/ this “problem”
19Stripper
Member
It sounds like the "mosquito" ringtone that some people cant hear. Might be why some people have never heard it. I think they all do it. I know mine does. It sounds like a high pitched ear ringing.
19Stripper
Member
Furthermore, mine did it the day I bought it with 16 miles. It isn't a failing part. Something with fuel system pressure is my bet.
Just a thought. It’s easy to diagnose/recreate with a simple vacuum hand pump. The IWEs won’t grind until there is a complete failure and they go left unchecked. When your truck isn’t running the IWEs are engaged. Start it up the vacuum disengages the IWEs (2x4). Then depletes the air in the larger vacuum reservoir. When you turn the truck off the vacuum releases and the IWEs engage (like when you shift to 4x4) the reservoir will continue to move back to ambient pressure.
Todd Sherman
Full Access Member
I have 2019 with 1300 miles on it, I don't hear this noise at all on my truck.
Matt Stachowitz
Member
My 2020 raptor, purchased new, now has 1,000 miles started making this “chime” when fueled up with premium gas for the first time last week. Any updates ideas causes fixes?
Oldfart
FRF Addict
I never heard that in my truck. I get a slightly different whistle type sound occasionally in my 2020 802A. I'm pretty sure I have traced the noise in mine to the rear.
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Yay - finally found some place on the Interwebs discussing this. I have a 2020 F-150, twin-turbo V6 eco boost with 10sp automatic, etc., etc. Live in AZ, and first noticed this a few weeks ago when camping in a very quiet, remote area of the desert. Noticed it again when out camping a couple weeks later, and then 2 weeks later while camping, then this weekend while it was just parked in the driveway. In each case, it had been off for several hours. Noise is very electronic, sine-wave, intermittent. Seems to start just before sunset and goes on for several hours. Truck has barely 2000 miles now. Otherwise runs great. Have not yet asked dealer. I have an iPhone voice memo recording, but I'm not tech-savvy enough to upload it just yet. I'll try to do that and add another post.
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