Single clunk when I accelerate, faint clunk when decelerating

I want to preface the problem description with a recent service note because it may be relevant...

I had a wheel bearing go out on my 2014 Prius V (106K miles). I decided to do both bearings at the same time, and that didn't go well. The OEM Toyota nuts buggered the threads on both axles, so I had to replace both axles and the oil seal on one side. The axles and wheel bearings are aftermarket items that had good reviews (don't recall the names). That job was done probably 1,500 miles ago and my son hasn't reported any issues with the vehicle (I don't drive it often).

This weekend, I decided to drive the car and on acceleration from a stop, there is a single click/clunk that can be both heard and felt. It is not related to engine speed or vehicle speed. Rather, it seems like the severity of the clunk is a function of acceleration. Even with moderate acceleration, I can actually feel the clunk, albeit faintly, through the bottom of my feet. I believe the clunk originates from the left side, but I am not 100% sure.

I can hear a faint click (but cannot feel it) if I brake moderately aggressively. The best way to describe all of this is to imagine a post in a hole that *should* have a rubber bushing around it but that bushing has disintegrated. Now imagine that when you accelerate, that post moves to one side of the hole and hits the side, thereby making the clunk (both audible and capable of being felt). The car tracks perfectly on the road (including freeway). There is no shimmy or other untoward behavior. The only gripe is that clunk... It definitely isn't normal.

I took off the wheel and confirmed that the four bolts security the hub to the car were in fact, secure. That proved accurate. When originally installed, I torqued them to the proper Toyota specified values along with the hub nut. I also used anti-seize compound on the axle splines when I mounted the hubs. I then reinstalled the wheels and test drove the car... The problem remained the same. At this point in time, I began to suspect the suspension....

I did not lift the car, but I did turn the wheels to both extremes so that I could look at the various suspension components. As best as I can tell the two rubber bushings on the lower control arm look OK. The rear one is the one that I was wondering about the most, and it is definitely centered both horizontally and vertically. I could not visually identify any cracks in the rubber, although I wouldn't call this a conclusive determination. The bottom of the lower ball joint looks like it may actually have some cracked rubber in there, but it could be crud. The top rubber looks fine. There looks to be some evidence of oil/grease stain below the outer boot/joint of the sway bar link on the left side. I couldn't really see much on the right side.

So, that is about it.... I'm guessing that is *might* be a suspension problem, but I'm posting this on PriusChat because I frankly don't know if that is true. I'm not a professional mechanic, but I am pretty ambitious and very good mechanically. I also know when to ask for help....

So... If any of you have ideas or questions, please let me know. I'll do my best to answer the latter.... I appreciate your help!

 

I didn't write this very well....

I took off the wheel and confirmed that the four bolts security the hub to the car were in fact, secure. That proved accurate. When originally installed, I torqued them to the proper Toyota specified values along with the hub nut. I also used anti-seize compound on the axle splines when I mounted the hubs. I then reinstalled the wheels and test drove the car... The problem remained the same. At this point in time, I began to suspect the suspension....
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What I meant to say is that there are four bolts that secure the hub which was replaced 1500 (+/-) miles ago. Those had been torqued and are not loose now. When I replaced the hub, I used anti-sieze compound on the axle/hub splines. After verifing the hub bolts were still tight, I reinstalled the wheel and torqued the wheel lugs; I then test drove the car and the thunk still was present upon start (this thunk is definitely not associated with the engine starting or anything like that. It is purely an issue of "something shifting." At this point, I began to consider what else might cause the problem and began to suspect the suspension...

 

Thanks for the response.... The axles, which include the CV joints as a unit, were all replaced with new (albeit aftermarket) units only about 1500 miles ago. That is *awfully* fast for the CV joints to fail. I'm familiar with the ticking or grinding noise, exacerbated by a far right or left turn, when a CV joint is bad. The noise I'm getting is nothing like that. It is literally a single bump, almost like a par running against a stop. It is most prevalent when I start from a dead stop, although I've been able to "trigger" the same noise by a fairly aggresive slow down and then acceleration. A coasting slowdown will not trigger it.

I've checked the CV boots and they are still in perfect condition.

I'm not too sure what you mean with regard to the brakes. The Prius V doesn't have any springs in it, although there are four retainer clips on four tabs. These are at the top and bottom of each pad. Those were installed when the brakes went back into the car. The shim pads were also installed. For lack of a better term, there were no "left-over parts", so to speak. If you can clarify what you are talking about, that might enable me to better ascertain if I failed in some fashion. Oh, calipers and cage were all torqued to Toyota specs during the job.

 

So, I finally broke down and took the V to a shop. They found the issue in a pathetically short period of time, although it baffles me....

The problem was with bolts on the right side hub being a little loose. Now, in fairness, I really thought the issue was on the left side, so I actually only confirmed that they were tight on the left side. When there was no difference in the behavior, I assumed I was on the wrong track. In retrospect, I realized I should have checked the right side too, but over there I only confirmed the brake caliper and cage.

Here is the part that baffles me though. I am absolutely certain that I torqued both the left and right to the specified values in the Toyota manual (if memory serves me correctly, that is 30 ft/lbs, which honestly always felt low...). I have that checked off on the list I did just to be sure I torqued everything down. So, I'm a little baffled. It *might* be related to the copper anti-seize around center hub area (to prevent future rust). Maybe that squished out during torque down, and then squished further, thereby rendering the original torque inadequate?

I asked the shop what they torqued the bolts to and the guy said that they used an impact wrench. hmmmm.... I like the idea of adhering to the manual, but aside from that issue, I do have to say that they absolutely nailed the problem. I get zero "thunk" now.

So... bit of a mystery as to why the bolts were on the loose side.... Oh, and should anyone be curious, yes, I did use blue locktite on them when I originally installed the new hub. And I heard no thunk for the first 1500 miles after that job (confirmed this with the primary driver of the vehicle).

 

Unfortunately I didn't mark down in my checklist the actual value, only a check that I performed the action. The 30 is my memory. I am certain that I did use the value on the Toyota sheet though.

[edit] You are talking about the lug nuts... Yes, those are 76 ft-lbs. Because I rotate tires on a regular basis, I'm definitely dialed in on getting that torqued properly. And, contrary to the wheel bearing bolts, I checked all of the lug nuts (front and back) when I was investigating the thunk. They were all fine.

The issue that resulted in the thunk turned out to be the wheel bearing hub assembly bolts. These are the ones that were apparently loose. And I checked my Toyota docs and they are, indeed, 30 ft-lbs. But here is the rub. My documentation is for the 2010-2015 Toyota Prius, not specifically the 2012 Prius V. I've never been able to find a manual specifically for the V. So, in retrospect, *maybe* there is a difference there? Most of these parts are interchangeable, however, so I seriously doubt that you'd find one at 60 ft-lbs and the other at 30. Still, it does give an uncomfortable feeling.

But, back to the point at hand, the lug nuts are not the nuts that the mechanic said were causing the thunk. The culprit were the four bolts holding the hub assembly to the steering knuckle

(I just tried uploading a file that showed the torque values, but I'm getting an 'unable to upload' error. )