Sounds like Yaris downshifts when I brake going down a hill?

[Nina88]

Hi there fellow Yaris owners! I have been driving my automatic 2007 Yaris for just a couple of months. It has 140k miles and previous owner took very good care of it.

Lately I've been driving a very hilly route to work and I've noticed that when I'm going fast (~50 mph) down a hill, when I put on the brakes, the car sounds like it downshifts to a lower gear. It just makes a sound like the engine is revving, and it keeps making the sound after I take my foot off the brakes. It will continue for maybe 10 seconds while I'm coasting downhill and then it sounds like it upshifts and the noise stops. This always happens consistently when I brake while going down a big hill.

I've heard of people downshifting while going downhill in a manual car so that you don't have to apply the brakes as much. I'm wondering if the Yaris does this automatically somehow? Does anyone have any idea what else might be causing this noise?

Thanks in advance!!