Knocking Sound on 2018 Prius Three

The Prius transmission does not really have a neutral or a clutch so to simulate neutral there has to be a careful balance of one of the MGs and the ICE. When the ICE starts there will be a small imbalance which will be felt as a surge. There is some play in the parking pawl which allows some rocking so whenever the iCE starts your Prius will rock and there will be a clunk from the parking pawl and the drive train. You can ignore it as it is unavoidable.

JeffD

 

When you turn off power the parking pawl will engage anyway. If you use the parking brake, the Prius will not rock when the ICE starts and your symptoms will be gone.

JeffD

 

How many miles on it?

 

Will milage decide if there is a sound or not?

Had an interesting sound situation, came in from a trip and when I got close to home, all of a sudden there was a horrible rubbing sound at the rear passenger fender, stopped to check and didn't see anything at first, then found a plastic piece at front side of bottom of rear wheel well had flipped sideways and was contacting tire. I have no idea what the piece was, or what it does, almost like a spacer piece at bottom of wheel well, just spun it back in place I think, but that cured that sound.