My neighbor and I have a similar problem with our Prius’. At around 35,000 miles, after an oil change at a dealership my 2011 Prius had a loud rattle while driving on a famous grade in my county called “Waldo Grade”. It may be known as “Robin Williams’ Tunnel”. There was a loud rattle that occurred from the rear of the car and goes away on the flats. I brought it into a Hybrid Shop and the proprietor drove it for a day and reported that he could not duplicate the sound. The noise has since disappeared and now I have 39,000 miles on the car. My neighbor had the same problem with his 2015 Prius: around 35,000 miles, after an oil change at his dealership, loud rattle and banging near his rear brakes. But his rattle occurred while braking down the San Francisco hills in the rain. My neighbor brought his car to his dealership and with this complaint and they reported that their driver was unable to duplicate the condition. He’s waiting for another rainy day in San Francisco but it’s unlikely that it will be soon. Has anyone had this same intermittent rattle and has anyone solved the problem? Is there any connection to the similar miles or oil changes?
Odd, for it to stop, and to happen on a near-new car. Have you posted this on Priuschat?
One thing you could do yourself OP, empty the trunk of everything in there, including the spare tire and jack, and see if the noise goes away then. One time I had a golf ball get into the rear wheel well area of my Corolla’s trunk, and it made banging noises during turning and when going over bumps while going downhill that sounded like it was coming from the wheel.
Two different year vehicles so I doubt if they both have identical rattles or noise from trunk contents.
@Anadale- You can also try toyotanation.com- it is hard to navigate but it does have a Prius board.
Braking while going down hill in the rain? You may be listening to the ABS brake system in action.
Haven’t had any similar noises from my mom’s 2010 Prius with almost 60,000 miles but the last time our mechanic couldn’t reproduce the problem (on her previous car) she drove the mechanic around on some nearby roads until he could hear the noise.