Ok i own a 1999 Expedition 5.4L Triton and well every time i drive the car a release the accelerator i hear a whinning or wistleing nosie. Its very faint but annoying and when taken to the shop they said they heard nothing. Does anyone else hear this same noise or other noise. This is my first V8,

 

it may be from the intake mandifold
is it made out of plastic ? lol

 

I have a 2000 but have never heard that before. Maybe a vacuum leak? If you can't get it to do it standing, it'll be tough to find out.

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2000 EDDIE BAUER EXPEDITION 4x2

• Estate Green
• 5.4 ltr
• 3:55 LS rear
• Superchip!
• Airaid FIPK
• Gibson S/S Swept Side Cat Back Exhaust
• Hellwig Rear Anti-Sway Bar
• Tow Package
• Rear Load Leveling
• Moonroof
• Century Child Seat!
• Front Polyurethane Anti-Sway Bar Bushings ordered

-->Come share my Addiction<--

 

its your gears; TRUST ME!

it happens when you coast and slow down, it sounds exactly like everyones problem in the link below

i have this same problem with mine... look at this link; it might give you some better understanding:

https://www.f150online.com/f150board...ML/000758.html

 

I agree with Tallywacker. It's the gears.
In particular it's LS gear sets. My toyota 4x4 did it when I switched to LS. My Supra did it with it's LS differential. Will everyone hear it? Maybe, maybe not. I'll bet that 95% with LS will hear it.

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1998 F-150 XLT 4X4 supercab flareside
Bright Red, Med graphite 60/40 int
4.6L V8, Auto, 3.55 rear, HD/Tow pkg, ORP
Slider, Keyless entry/Alarm, Pwr/W/L/M/S

ADDED

Uniden PRO520XL/Wilson 1000 CB
Alpine CHM-S655RF 6 CD changer