97 4.6 4r70w 4x4.
For as long as I can remember I would get up to speed around 55 and my truck would shift into the highest gear and just cruise along at around 1200 rpm.
Now, the rpm's will be at around 1500 rpm.
Something changed.
I'm not certain if it's shifting the same or not. Was thinking maybe a shift solenoid has failed....just a guess.
Any ideas?

 

You know there is Converter lockup in overdrive supposed to take place!
It's not locking up.
This allows the Convertor to fluid slip, that increases the engine RPM about 300, .and generates more Transmission heat, and reduces fuel mileage.
If there is a fault present, a Code in the P 0700s should be present Describing the lock-up fault.
I see its 6 mo.+ ago you might want to know about it.
Good luck.