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!

[BR3W CITY]

Have you hooked it up to HPT or a pro-style scanner that can read/command trans codes?

Any chance your harness is pinned-out wrong and one of the solenoids is getting a signal it shouldn't?

[67Steven]

Originally Posted by BR3W CITY

Have you hooked it up to HPT or a pro-style scanner that can read/command trans codes?

Any chance your harness is pinned-out wrong and one of the solenoids is getting a signal it shouldn't?

I do not have access to one of those readers, but I guess I can try to locate a mechanic with one to try that out.

As far as wiring, it is the original harness, and nothing was changed at the transmission, so I am going to speculate that it is okay. I am just worried I will need to replace the solenoid pack/TCM unit.

[Houston Ben]

My 6l80e has a high whine in 1st but that's it

[clinebarger]

Originally Posted by 67Steven

I do not have access to one of those readers, but I guess I can try to locate a mechanic with one to try that out.

As far as wiring, it is the original harness, and nothing was changed at the transmission, so I am going to speculate that it is okay. I am just worried I will need to replace the solenoid pack/TCM unit.

The TCM is staying "Awake" for some reason, Most likely a wiring error,
There is a Pink Ignition Hot wire at the Trans plug, This wire should only have power with the key on.

Don't replace the TCM!!!!

[67Steven]

Originally Posted by clinebarger

The TCM is staying "Awake" for some reason, Most likely a wiring error,
There is a Pink Ignition Hot wire at the Trans plug, This wire should only have power with the key on.

Don't replace the TCM!!!!

Sweet! I will check the wiring to see if it is staying on, well verify that is the issue. I have a relay from the ECM that turns the trans on and off, and I can hear it click that off, but I guess I have something incorrect.

I will update when I figure it out.

[Chvy2NV]

Any updates?