'05 tranny question

I have an '05 silverado 5.3L 4wd and have a very noticable whine in the transmission when towing anything, light or heavy in tow/haul mode. Often times it will continue for a day or so following towing something. The truck has 31k miles, I've had it in the shop twice and they cannot replicate it. Just wondering if anyone out there has had the same problem or if anyone knows what may be causing it.

Try a different dealer, drive it around and make it do it and then take it in.