If I scan shift times, shift time errors, or anything else useful can I determine the health of the transmission? Is there any general number or combination of errors generated that would say a certain clutch pack is wore or the valve body is dirty or just give me a specific area on where to look for an issue?

The reason for this is that I have a stock untuned 6L80 in our Denali that had a fluid exchange a year ago prior to purchasing and the fluid doesn't look a year old. I have a very hard 2-1 downshift when coasting and a couple 2-3 flare ups every now and then. I have heard these trans have a history of this without actually having any thing wrong with them. When I tow my trailer, the Tow Haul mode might as well be dump truck mode for how aggressive it bangs shifts. I wanted to see if the scanner can give me a little more info as to if its just a dirty valve body or if a certain clutch pack is wore. Or should I just throw a tune in it to soften up the down shift?

Any info would help. Thanks!