I used my OBD II scanner to read the transmission temp in my 97 F150. Driving today in about 80 degree weather I peaked at about 155 degrees and coming home tonight at around mid 60's i averaged between 128-138. I have a pretty big aftermarket cooler working in tandem with the factory in radiator cooler. Are these temps optimum? I have heard it's not good to exceed 200 degrees but im not totally sure...

 

170 is about the average under normal hwy driving [no trailor] so your cooler is helping