I am thinking it could be the rear sway bar bushings. Not sure why the sway bar would need replacing.

 

 

 

Normally there are two rubber bushings that surround the sway bar and are what the mounting bracket holds onto to constrain the sway bar movement. Over time, the bushings can degrade and allow movement of the sway bar as the car runs over bumps and other road imperfections. This play of the sway bar make noises.

I can't imagine why a sway bar would need to be replaced for routine maintenance. maybe Lexus wanted to replace the bushings and added the bar to pad the price. Interesting that Toyota did not find it necessary. But I would speak to your mechanic about the bushings and see if he checked them, and ask him to price replacing them. If not too expensive I would have him replace them.

Another option is to find a tire center that is highly rated on yelp and have them do a diagnostic examination. They often get suspension type complaints as a routine (due to people thinking it is related to the tires, balancing or alignment), and may be better equipped to figure it out. And would be another opinion to balance against the others. If you do go to one, do not say you have had it looked at by anyone else before they diagnose it. Only bring that up, if at all, after they tell you what they think is wrong.

 

 

 

Seems crazy to completely remove the sway bar.

Did the noise go away once it was removed? Are you ok with the handling of the car without the sway bar?

 

That's what I thought. I asked him to put it back on with new bushings, but he said it would not help or make a difference, so I didn't insist. I plan to insist he do it now..
As far as I know, the car has not felt different driving it, but it hasn't been taken out much lately.
Thanks to everyone who has responded.

 

Interesting, i have a 2008, and also replace the rear sway bar bushing, from ebay, i think there's only one sellor that have it. worked great. I also replace other rear bushing around the wheel base. A simple mechanic check up can determine source. The bushing does cost much, all in the labor.

 

The sway bar bushings would have to be significantly worn down to be causing that noise. You can remove the sway bar completely to see if the car still makes the noise. The car can safely be driven without the sway bars which are designed to reduce body roll when cornering - so, don't do any hard turns with the sway bars off.

I'm thinking something is not tightened down properly. A sway bar link is one possibility; also, strut bolts, spare tire hold down. Also check for a broken exhaust hanger(s). Worn out engine and/or transmission mounts, and LCA bushings can also cause a similar sound. Good luck; let us know what you find.

 

Update: I took the car to a very reputable tire store for their opinion about the loud thud that continues to occur going over bumps. They checked all of the suggestions that I've gathered here and could find nothing. They even had someone sit in the back seat while the car was being driven to help identify where the noise was coming from. It's definitely coming from the rear of the car. Nothing in their opinion would account for the noise heard. They suggested that we wait and see if it gets worse/louder which is what we've decided to do. Very frustrating. Thanks to all who've contributed ideas. I think I've followed up on all of them.

 

 

Yes, I check the trunk. the spare tire was not loose, though there was a set of jumper cables that might have caused some noise. I secured the jumper cables, but no difference in the noise. Thanks

 

I forgot to add that the tire store where I last took the car, suggested replacing the rear Trailing arms (MOGRK641472

I read somewhere that it might be worth trying. what do you think?