Strange noise while cruising???

[specTAKular]

I have a stock '00 GT vert and it seems that any time I am going anywhere from 35-65mph and I let off the gas it starts to whistle, or make a 'whizzzzz' sound. I have all new brake pads, rotors, calipers, and hub assemblies on the front, but the sound was apparent before all this was done as well. It sounds like its right under the middle of the car, so I'm wondering if there is something in the trans that is spinning free when not accelerating.
It stops as soon as I hit the gas or the brake.

Any of this sound familiar???

 

[Duke309]

Might be your gears in your diff whining?

 

[specTAKular]

I don't believe it's in the gears. I had a cert. mech. switch out my diff. oil and he said the gears looked good. The sound seems to be coming from closer to the engine in my opinion.

 

[StangPro]

To you have a TB/plenum on the car? Many make different noises.

 

[specTAKular]

everything on the engine and trans is stock. it's also an automatic, if that helps.

 

[specTAKular]

anyone else have a stock TB/plenum that makes such a noise, or any at all?

 

[DocG]

Does the car seem to shift like normal? So it doesn't make that noise any other time? Rev'in it in neutral and letting off the gas?

 

[specTAKular]

no, it's only when i'm not accelerating...and the faster I am going, the more apparent it seems to be. When I brake, it still seems to be doing it, but very faintly.

It does seem like it could be the plenum, if the butterfly valve is not closing properly. Anyone else have this issue on their stock plenum, or in the throttle body?