Noticed Something Odd.....

I had my truck do something it hasn't done before since I've owned it over 9K miles. It's a 2017 Tacoma Double Cab automatic. I was driving in some fairly hilly terrain at probably 45 mph. Once I hit the steep downhill, the trucks RPMs increased and kind of took over even though I wasn't depressing the pedal. Is that normal?

 

Yes.

 

Pretty sure you are describing engine brake. It's so you don't have to slam on the brakes and helps keep the brake pads from wearing fast.

 

AI shift control.

http://brockandbecca.com/files/fj/Technical Service Bulletins/auto_transmission_ai.pdf

https://patents.google.com/patent/US7695404

 

Definitely normal - and one of the few, if only, features I actually don't dislike about the transmission.

 

It was just odd, which this is the first actual new vehicle I have owned. I expected to just coast down the hill with the foot off the gas, but the engine took over and kept speed.

 

yeah, I drive in the mountains quite a bit and generally had to throw it into a lower gear going down mountain grades or end up riding brakes. my truck has always done a pretty good job of downshifting to 3rd on it's own going down the mountains, minimizing braking - of course when it gets REALLY steep I'll still take it down to 2nd but 90% of the time 3rd is perfect