6L80 transmission whine at shut-off

[67Steven]

I have what I believe to be an issue with my transmission. When I shut the motor off, the trans produces a high pitched whine.

It is a 2008 L92/6L80 combo out of a hummer with 13K miles. Both components are from the same truck, as is the harness.

I have done a multitude of searches, and I have discovered that this is supposed to be normal- it is the solenoids 'equalizing' pressure and it should shut off after a minute or two.

My transmission whines for hours if I let it, even overnight as I once found. No codes have been thrown, and it seems to work okay, although I have only moved it down the driveway and back a couple of times. The whine stops as soon as I interrupt power either by the ground cable or the trans plug, and stays off until I turn the key on.

Anyone else have or had this problem or know what it might be? Again, any help is appreciated!