Transmission whistle/whine

[FIELD8585]

I recently did a 87octane tune (standard, no changes) and now after approx 5 minutes of driving I get a transmission whistle or whine that changes pitch with RPM. If I shutdown and restart after sitting 1 hour the whistle is gone at startup but returns shortly after driving. I have a 2006 Avalanche with L33 engine 4I60 trans. What would cause this issue, the transmission doesn't do this on the OEM tune? I also noticed an abrupt 1-2 shift at 2000 rpm.

[mikel]

Cant say I've ever heard of a situation like this. Have you returned to stock to ensure the sound goes away?
Is the hard 1-2 shift every time,or just when its cold?

[FIELD8585]

Yes, the sound doesn't happen with the original tune. The hard shift stopped after I went back to original tune, then reinstalled the Diablo tune, but the whistle/wine is still there. Oddly enough it doesn't do it consistently like it did on the first uploaded tune. Now it only does it every second or third time I drive it. I also noticed it will start doing it sooner if I hit the gas and higher rpm is applied. Not sure exactly what is causing it.

[mikel]

load the tune and post the last tune written file from the tunes folder and we'll check it out to see if anything odd stands out.

[FIELD8585]

As odd as it is I found the issue and it wasn't the tune, at all. I just swapped in a L33 to replace the LM7 and am now experiencing a ground loop issue. The owner of the L33 mentioned to me today that he had the same whining for years. I will be putting my old alternator on which I believe is the issue. Thank you for your responses, much appreciated. And I can tell you that since do the canned tune I am experiencing a 4 mpg savings. Happy customer.

[mikel]

Glad to hear it!