Hello!
My 2013 Scion TC seems to be trying to shift between 40-45 mph or around 1500 rpm's . I just recently had 100k mile maintenance and it still seems to be the same.
When I put it into "sport mode" there are no fluctuations with the rpm.
Thank you for the help!
Your transmission is somewhat worn inside. I often see that that when you put it in sport mode all the problems go away so I would just drive it that way myself if I were you