triops44

Sounds like a plastic knocking in the right rear side. Almost sounded like something knocking in the trunk but cleared it. Inside the cabin it sounds almost plasticky knocking, at first I ignored it because it sounded just like a loose plastic cooler lid knocking.

It actually doesn't need a big bump to hear it, it's loudest going over small hills in the pavement just enough to jiggle the suspension a little bit, also going down small ramps, making turns etc. I notice it most at low speeds around the parking garage most, maybe because it's harder to hear at highway speed tire and wind noise, and smoother roads.

I have bought sway bar bushings, sway bar end links, and also rear struts because they have about 100k miles on them and both boots are torn but I didn't see leaking, and thinking it might be the strut mount, but not sure, going to take them to get installed but wanted to check if anything else looks worn. Could it be one of the rear control arms? I'm trying to make sure it's not a more obscure issue, I just found out that these cars might need to have rear knuckle bushings replaced which are hard to even source but apparently may be a common "niche" issue to these cars?

It's not a metallic rattle or so at first I really thought it was some loose part in the under trunk floor storage since those bins are plastic, but I have tested that. I also checked its not the sunroof. The video doesn't really replicate what it sounds like in the cabin bump recorded it to see if anything obvious could be the culprit?

Forgot to add, car has about 180k miles

Felix

More then likey the one of the rear sway bar end-link's if not both.........

Leeper

IFit turns out your rear sway bar links are bad (at @20 years old that is highly likely) go look at Matt's post he researched this and came up with a brilliant solution for a raplacement that saved me $$$. If I were anyone on this forum just due to time this should be a replacement item even if they appear to be in working order. Very quick and easy to replace also cheap though mine required using my grinder as the nut was rusted but still only took maybe 30 mins total for both sides.

davintosh

Sorry to tag onto your thread, but came here looking for help with a similar issue with my 2006 RX400h; low-speed clunking in the rear.

I changed the rear struts before the noise was noticeable, and my first thought was that something was wrong with them or something had come loose, but everything looks normal and makes no noise with the usual tricks to find suspension issues with the axle in the air. Also changed the sway bar links; seemed quieter for a short time, but it’s back. It had a towing hitch on it that was quite corroded; removed that to refinish it. Again, the thumping seemed better for a short while, but came back.

I’m tempted to just replace everything with rubber on it on the rear axle (it’s got 200,000+ miles), but I’m hoping that someone might have some better ideas to narrowm down the list of suspects.

Leeper

Try twisting your sway bar links, if they can be remotely easily twisted at all they are shot (some aftermarket brands are terrible and give way within a years time), might want to also change out the sway bar bushings themselves (extremely cheap). There is a rubber padding on the strut between the srping and the cup it rides in not sure how you'd check that but they are wear items other than that I'd go through to assure all my nuts/bolts were proeprly tightened (there isn't many at all). I've seen simlar issues on other cars remedied by using silicone sspray on rubber bits

headwest

Mine was the sunroof gasket being worn causing rattle

SeaLex400h

Leeper, I'm a new ClubLex member and the site's a bit of a maze: can you share more info on how to find Matt's post on the sway bar solution? Link? Matt's user name? Thanks.
I can tell this is a great site with lots of generous folks. Wish I was 28 rather than 68: might be a bit more spry getting under my car....

Leeper

Here's my order from Amazon for rear sway bar links, they worked p[erfectly for my RX330 I believe they are the same for the RX350 but do your homwork (check the length). Not sure if I mentioned it they are very easily and quick to replace even for a 68 YO no need to get under it they are accessible from removing rear wheel, skill level is a 1 unles you have to cut off the old link then a 2 as mine were rusted on so it took me a total of maybe 30 mins to do both - [url]https://www.amazon.com/gp/product/B06X6CW7SV/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1

Here's the link to Matt's numerous projects, there are many, many great tips and tutorials here it is a wealth of info at a high level of mechanical talent.
https://www.clublexus.com/forums/rx-...0-project.html

Good luck let me know if I can help in any way