I took my 18 gmc 6.2 8spd with 5000miles back to the dealership today for transmission problems flair-shift,delayed-engagement and not downshifting at stop signs. They couldn’t find any problems ( big surprise). My truck was driven a total of 2.8 miles! How can you check for transmission problems in that short of a drive? They only looked at the truck after I arrived the dealership 8 hrs later when I got in the truck to leave the trans temp was on 137 degrees! So GM techs can you diagnose transmission problems on 2.8 mile trip with the transmission not up to operating temperature?