I use my scan gage II for this data. You have to add it as a custom code, but it works like a champ. Yes the mountains around Gatlinburg and up through Kentucky had me slowing down a lot to keep the transmission below 200. I also monitor fuel consumption with it as well. It's not entirely accurate, but it's close enough.
Carl & Dawn
2015 Greyhawk 31FS
2015 Ford Transit Connect (our TOAD on a DEMCO Dolly)
DW, DSx2, DDx2 Catx2 Dog
Tampa Bay Area of FL