I have a 2018 RX 350, 3.5L 6cyl, 80k miles, with an audible (but not loud) clunking from the rear end at slow speeds and uneven pavement/bumps. Sounds like it’s coming from the rear passenger side. I’ve been having trouble diagnosing and resolving this issue, especially since I’ve replaced both rear shocks (w/ KYB) and rear sway bar links (w/ MOOG), the sound is perhaps better but still persists. Today I was under the thing again with a flashlight, and noticed cracking/rotting of the rubber of the lateral control arms. The condition of both arms is worse on the side closest to the wheel compared to the side closed to the center of the vehicle. I’m wondering what you all think about how they look - could they be the culprit?
Attached image is Driver’s side…passenger side looks the same.
RockAuto part link just for completion sake: MOOG RK642987
Hmm, interesting. Initially I thought it could be the bushings because there’s a minor gap around the edges, but convinced myself that was unlikely since the car is a 2018 and only had 72k on the clock when this started. In other vehicles, I haven’t had to replace the sway bar bushings until well after 100k. And anecdotally the fronts are the first to act up.
The bushings look like they are definitely worn, but they might not be cause of the clunk. Does the clunk sound more like metal hitting metal? Or more like a “whump”? What condition do you notice it most? When braking, when turning, when moving at higher speeds, at lower speeds?
I had a whump whump whump sound on my Corolla , most apparent when turning at a low speed, like inn a parking lot, turned out to be a tire problem. Anything unusual with the tire treads? If tires are nearing time to replace anyway , might be a good idea to start there, might get lucky and solve the problem.
Thanks for the response. It doesn’t sound quite as harsh as metal on metal. Happens at low speeds, most noticeable when going straight or turning on roads with small bumps/unevenness. The tires are a good thought, but they are new Kelly’s with less than 10k on them and there are no signs of uneven wear.
I’ve ordered a pair of rear sway bar bushings (interestingly, no aftermarket parts for this model. Have to buy directly from Lexus). We shall see how things go. Got underneath and tried to get another photo to get a closer look:
Seems unlikely to be a tire problem then . Your photo is showin more space then I’d expect to see. Even on my 50 year old truck (with no clunks), it is showing signs of needing a few new bushings, but nothing like that. Maybe there’s an easy test to tell if that’s the problem or not.
To follow up on this - I’ve now replaced the sway bar bushings but the sound persists, no change at all
Worth mentioning - I first noticed the sound after I replaced both rear shocks about a year ago (FCS parts). I had not loaded the suspension when torquing them down, so I replaced them again a couple months back (this time with OEM KYBs) AND loaded the suspension before torquing. I noticed the sound disappear for a about 100 miles or so, but it returned just the same.
That seems like a very important clue. I expect you are close to a solution. And at least you have new sway bar bushings. Has a pro shop tech had an opportunity to use their standard pry-bar diagnostic techniques? If not, that seems like the next step.
Just to clarify - it was after I replaced the shocks most recently that I noticed the sound briefly disappear (your quote says sway bar bushings )
At this point, the vehicle has new: rear shocks, rear sway bar bushings, rear sway bar end links. All of this started after I replaced the original worn out shocks (Hitachi/Tokiko for this model) with a new pair (initially FCS, now KYB).
)