Tranny issues

Hey guys im having some tra ny issues 15 ram, hemi, 8spd. Not sure whats going on but its not bad but its also not normal. I dont haul much but I drive 90% hwy for work cruising at about 115km to 120km. I use to just drive in D all the time but have this annoying thumping downshift from 8th to 7th when i touch thethrottle. Very hard to replicate seem to only happen once in awhile. But def dont feel right when happens.I can feel it thru the whole truck. I think its too high of a gear honestly and maby just i have a bad tranny? its flash updated only 30000 km. I dunno if its normal but it ****** me off. Truck runs like a dream other than that. I did have the truck flashed for 35's so my speedo would correct and never noticed this happening till after.
Try driving in towhaul mode and the dam truck still shifts into 8th. Im not sure if its an internal issue. I think its a cpu issue since I cant replicate it. And i manualy leave it in 8th and downshift to 7th, i cant get it to do it. Its strange, but its ruining my affair with my truck. Because other than that ive been blown away by the truck.

Help? advice? thoughts?
thanks

Yeah mine does the same.There's one spot on a local 4 lane that it does it pretty much every time.Slight grade and light throttle load at approx 70 mph.Saying all that it's done it less than 10 times in a year and a half(14k miles).I very seldom ever travel that road and annoying as it can be I'd sooner live with it then have FCA screw with it because it works so well otherwise.Probably not what you wanted to hear,but that's my take.