I have a 05 trailblazer with a 5.7 vortec When eng is first started and shut off there's a noise like a fan whinning down for a few seconds This noise disappears after eng is warm I removed the belt and I still get the same result

 

trans

 

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I agree with "hucks 66", it may be a transmission related. The may be an issue with the drive, drive sprocket support bearings or gear bearing. This is just a suggestion, not a diagnosis. I encourage you to have the vehicle inspected by a certified technician for an official diagnosis.

Please keep us posted.

If you have any additional questions, please feel free to contact me.

Louis
GM Customer Service

 

when I remove the elec throttle fuse it stops the whinning Does this help the diagnosis