Maybe someone has had a similar issue. 2004 RX AWD. At highway speeds I hear a rattle from what appears to be under the vehicle. Almost like if one of the pieces of plastic which go under the engine is missing a screw. That is not the case. It sounds more like it is coming from under the driver seat area. Any suggestions would be greatly appreciated.

Thanks

 

You sure it is not the infamous sunroof wire that rattles only at certain speed like 45-55mph?

 

I posted a solution to this a few months ago after searching about the same noise. Long trip and the noise was under the drivers seat. The noise was driving me crazy. If you get under the car you will see a piece of plastic that is at least 3 inches away from the bottom of the car. I thought that was a lot of travel so was skeptical. I wedged a piece of styrafoam between the plastic and the body with glue on both side.

Noise gone.

I thought it was trim from roof rack flapping, had passengers reaching under the seat, etc, but the styrafoam block fixed it.

 

Does it only come on at a certain RPM. Mine had a rattle/vibration at a certain RPM and it turned out to be something loose in my catalytic converter. Thankfully Lexus replaced it as part of their goodwill.

 

I just had my dealer remedy that problem. Turns out it was the plastic cover by the fuel tank or something.

 

My rattle only happens at highway speeds. I am going to check plastic under car below drivers seat.
Thanks

 

This is the source of the noise you're experiencing. Mine suddenly started to "whack" the underside of my car under the driver's seat at highway speeds also. If you look at the plastic cover, you will likely be able to see the adhesive residue where there used to be a foam block. Put something similar back in it's place and your noise will be silenced!

 

I just took my 2007 RX350 in for the same reason, including the Upper Windshield "tick".

For the tick, seems they did pretty much what was outlined on the TSB L-TCI-3280 (UPPER/LOWER WINDSHIELD TICK NOISE).

The noise under the drivers seat was from some type of shield that came loose. They tightened it and I have not heard either noise.

Happy camper as frankly I was fed up with all the squeaks and rattles.

Even a 2007 with 73k miles should not have those problems.

 

Your styrofoam solution fixed my rattle which sounded like it came from the roof. Brilliant!!! Thank you so much