At HWY speed of 75 to 80 mph the RPMs are 3000. If the over drive button is depressed the RPMs shoot up to 5000 and stay there.
This car has no codes, errors or check engine lights on.

What can cause this?

 

It's downshifting. I'd be surprised if it didn't.

 

I was going by what my daughter told me was happening. It appears she doesn't know how the OD on her car functions. She pressed the OD button and the OD light came on so she assumed it was on however the other half of the equation was missed. Press the OD button and it lights saying OD OFF which is why it pegged to 5000. Thankfully it was that simple as I was thinking she had a transmission solenoid or torque converter going bad.