Clunking/clacking sound on acceleration and deceleration

A few months ago my 06 Prius began making a metallic click when slowing down or speeding up. This has gotten worse over time and now instead of a single "clack" it's 2-3 in succession. This doesn't happen when going over bumps like I would expect with a swaybar link or balljoint problem. I was convinced it was the lower motor/transmission mount from the symptoms... it made sense to me that as the engine tried to move forward/back a bad one would do that.

I got under the car and inspected it and found this piece of metal (bushing?) sitting on top of that mount. (put it back for the photo) It doesn't appear to have anything to do with that mount, but I can not figure out where it came from! I also took a large pry bar against the subframe and moved the engine/transmission and didn't get any noise. I have replaced an engine on a different Prius and the transmission on this one 3 years ago, so I'm fairly familiar with the ins and outs of them but this one has me stumped! Any ideas? Thanks!

 

Found it: Motor mount bracket help asap | PriusChat

Thank you! I wonder if this is the cause of my noise... something tells me no, but I may order a replacement mount anyways since mine is aged to the point of that piece falling off.

 

Got back under the car again and found that the passenger side CV shaft had a split outer boot and all of the grease had slung out. Replaced the whole shaft assembly and the noise is gone! I wouldn't have suspected the CV since I have only heard of them making noise when turning, but after some research it does appear they can get noisy when failing even when starting/stopping.