My K2500 has 103,000 miles on it. 4L80E transmission with factory tow package (tranny cooler). I tow often, and heavy during the summer. This summer so far I have towed about 10 times 1.5 hours each with 1/2 stop and go traffic, and 1/2 highway with some hard hills. I tow 6000lbs, which is max according to the manual with my 3.73 gears and 5.7 engine. The Tranny fluid and filter were changed last summer at about 85k miles.

Recently the transmission has been whining as the rpm increases. It is very noticable when towing, and now I have heard it when not towing too. No changes in shift points or hardness.

I am wondering what kind of failure I am in for and when. Any ideas?