Originally Posted by Bigfoot
I use syn blend oil
No unusual smells
Has never shifted into OD since that hot summer day
I always leave it in OD, and run it at freeway speeds (70+) and it never shifts to OD
No speedometer problems
Synthetic may be part of your problem. The TCC may be slipping too many RPM'* and can't lock.
No codes surprises me. That tells me either someone took your bulb out of the SES light, or the PCM isn't requesting OD for some reason.
What RPM do you run at 70?