That elusive 10th gear

First post. 2023 Double cab without hybrid. While highway driving in 2WD and transmission in D, at 1400 rpm I’m showing 68 mph. I figured that was top gear, 10th gear. Yet last week I tried the S gear option and found in S9 I also get 1400 rpm at 68 mph. Since the transmission in S range chooses the selected gear or a lower gear, this tell me 1400 rpm and 68 mph is likely 9th gear and definitely not 10th gear.

Is this logical?

I then accelerated to 76 mph and saw 1700 rpm. Changed from S9 to S10 yet no rpm change. And now selected D and no rpm change. Is 9th gear the “highway” gear?

Or was I shorted one gear on the assembly line?

Dave

 

Oops looks like it is addressed here. Short answer: one needs 75 or 80 + mph to get 10th gear

https://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwimrPWzx_qAAxXcg4kEHWT1AMgQFnoECBcQAQ&url=https%3A%2F%2Fwww.tundras.com%2Fthreads%2Floss-of-10th-gear.119236%2F&usg=AOvVaw03SKDxISZMdYaipfMi_OF_&opi=89978449