Ping like sound, but no pre-ignition

It started a year ago and it's getting worse. It's not really a true ping because it's not RPM or load dependent. It is actually worse with cruise control coasting down a hill with regeneration. It comes and goes, intermittent. Best heard between high 40's and low 70's mph. Never hear it in town/suburb driving. Only hwy. Car has about 72,000 miles. I cleaned EGR pipe, TB, and intake. No change. Seems to originate from tranny or left front corner. Doesn't come from engine the best I can tell.

Any ideas? Thanks.

 

Thanks for posting. The weird thing about it. it only becomes audible after driving for half of hour or longer. it doesn't sound like the typical rattling of something loose. It doesn't respond to road bumps or roughness. it really sounds like coming from the drive train, but left side. this makes me concerned enough not to take the prius for long hwy trips any longer before i fix this. It sounds similar to this recording (from a BMW, so a different problem of course):

 

update: i'm doing injector cleaning in this tankful. doubtful if that produces any results.

 

no difference. i'm thinking now it's mechanical and related to the CV ticking/clicking while slowing down while turning. i was able to hear the rattling in city driving for the second time now (i hear it on hwy near 70mph all the time, or at least some of the time) Both times were when turning right while going near 50 mpg (not common in city driving).

 

Yeah, it's getting worse and not hard to hear in city driving now, especially when turning. I'm thinking these must be the clicking CV joints that I had for a while. I'm kicking myself for not insisting on repair while under drivetrain warranty.

 

Folks, if I'm a persona non grata here, please let me know and I'll not bother you with my posts.

 

Boots are fine. I don't have the typical defective CV joint click. Just the soft ticking when turning and slowing to stop (described in a few different threads here). I had it for at least a couple of years. Only now it occurred to me there could be a connection to the fast ticking/soft ringing while turning at near 50mph or faster.

PS: thank you both for replying.

 

update: finally got under the car and removed the engine cover. everything is in top shape. however, when i wiggle both driveaxles hard (both side to side or up/down) there is some clicking noise in the outside CV joints. Can someone tell me if that's normal?

 

Mendel Leisk,
thanks for confirming that noise in the outer joins is abnormal. some other folks told me the same on another (non-hybrid) automotive forum. too bad I didn't think about checking that when i first discovered the ticking noise while under warranty. i seriously thought it was harmless and didn't want to sound paranoid to the dealer (who are always hearing impaired for those type of things).

 

Update, I came back from a long trip (1000+ miles), and I suffered from that rattling noise most of the time. I'm positive now it's CV as the noise was evident in every turn. Interesting, mpg went down a lot toward the end of the trip (below 44mpg, while the trip average was 48).

The next commute after the trip was also characterized by a lot of rattling on turns over 40mph and below average city mpg (low 50's). But, today rattling almost gone and city mpg went back to normal (high 50's).

I'm waiting for a super duper CV grease to get delivered before I attempt a fix.

 

if anyone cares, i opened both outer CV boots and the factory grease is in good shape (solid consistency and good amounts). This is not what i expected. i had issue in subaru that CV grease separated from oil and oil dripped from CV joints on exhaust pipe producing awful rubber burning smell.
i guess toyota used good CV joint grease quality and i decided not to repack with new grease (a messy procedure).

 

not wheel bearing noise. fast rattling noise. i can't believe i'm the only one hearing that.
this below (toward the end of clip) is not mine and mine is a bit different (faster and at higher speed), but this should give some ideas what i'm talking about. the noise is sensitive to steering input in the sense that no noise when going straight. no difference left or right.