It certainly could run that high.
Almost all auto transmissions are cooled by a transmission
cooler inside of the radiator, which in a car runs at 195f, so the auto transmission
must run considerable higher to be cooled by a cooler in 195 f water
I’m not saying that is normal, I have no idea what is, but 170f isn’t outside of the realm os possibility I wouldn’t think.
Call an overhaul
shop if you can’t find anything in the manual, they should know