I AM NEW. i AM MIKE JUST BOUGHT A USED 2018 F150 3.5 ECO BOOST 4X4

[mkedort]

TRANNY ISSUE : Driving frwy speed for about 3 hours with no load, the weather in the 70's and the ten speed tranny starts down shifting to 8th with a klunk then 7th back to 8 then 9 then 10 and does it again I check the temp 217 and it climbed to 224 with the tranny continuing to down shift and go back I put it in tow haul and it helped some , I got off frwy kept driving and it cooled to 203 and started shifting without klunking. Any sugguestions?