I wonder if anybody has this problem with their RX300.

When my RX300 go over humps 'thud' sound can heard from the undercarriage.

 

Is it a deep resonating type sound? If so, mine does it also.

 

There have been several posts in past on this topic. Sorry didn't get a chance to look back and provide you the link. Basically, the struts will need to be replaced, covered under warranty.

 

There is a fix for the front struts that remedied this on my car. What year is yours?
Bob

 

Bought mine in March 2001

 

Have you checked the spare tire cover? I have a 2001 and noticed the same noise. It was the plastic cover over the spare. I put some noise-dampening material (Dynamat from Crutchfields) on the underside of plastic cover and the noise went away. For right now try putting a towel over the spare and replace the cover. Just a thought!

 

Sky, I have done something similar and I am quite sure, having climbed in the back area while my wife drives (scary huh?) that the noises I have are in the door not the floor. The hanger and anything in the spare wheel area can cause annoying sounds so one needs to clean those issues up first.
bob