2008 Lexus RX400h Not Shifting to Overdrive** NO CHECK ENGINE LIGHT

This vehicle has an CVT - continuously variable transmission. It does not have an "overdrive" to shift into. What are you experiencing that makes you feel like this is a concern?

I am having the same problem on my 2008 rx400h. It has 122K miles and I had the transmission serviced at 110K. It drives fine up to about 45-50mph, then sounds like it's over-revving at any higher speeds. I know it has the CVT so no overdrive, but the symptom resembles a car where the overdrive is not kicking in. My gas mileage is still the same in the city, but on the highway it seems like it's dropped. This has only been going on for about two weeks. Was working normal before that. Any thoughts? Did Aamco have any answers?