L83 with 6L80 trans. After driving for about 2 hours on country roads and through towns, noticed that the trans was shifting differently in town. Caught off guard. After the 2nd time, I checked the temp. 190 which surprised me. Cooled to 181 after I left town. Repeated in the next town ( sluggish and 190 ) and when finally when I was driving around town at my destination temp got to 192 (and was sluggish). I had the trans filter changed at 60, 000 and thought I was ahead of the game. Only occasional light towing. Oil level is good. Have appointment at dealer on Wed. so I don't know if it caused a code or not. I am trying to do my homework before seeing dealer. Any ideas?