lizard-navy-keep

late to this thread but yeah replace ATF. you have nothing to lose. bought my truck with 5 miles and around 19k the 6l80 acting goofy. called dealerships to utilize my precious warranty and got told transmission guys are backed up 6 weeks and i'd have to leave the truck and no loaner. After losing my previous truck to the 6 speed rumble strips i started swapping out a gallon atf every 6 months and added the thermal bypass.