I week ago I bought my GX470. While I love the car I have run into one issue has has very quickly become a pain in the neck. After the first couple of hundered mile I start hearing a light knock underneath towards the back of the car. It started as a couple minutes apart but then grew to a regular knocking. It never affected the way the car drove. Speeds 30-70 mph it happens very regularly. Anyways I took the the car to the dealer. Just before I got there I had to make a sudden stop at a stop light and thats when I heard a loud metal snap in the back and the sound stopped coming. Of course the service guy took a test drive with me and never heard it. Turned the car in for the night. They looked at it , did not find anything. Guess what the sound is back again and again I hit the brakes and with the lod snap the sound is gone. Any clues.

Do you have the third row of seats in the up (not usable) position? One possibility is that the strap holding them is not tight enough and this is causing the rattling.

I have tried it in both positions. Up and down. It sounds more like it is coming from underneath the car.

Additionally it happens only after I have driven the car 15/20 miles in the day.

Your lexus tech doesn't know his GX470. The noise you are hearing from the axle shaft. Having too much clearance, so it's pretty much sliding back and forth. They will have a fix for this concern soon. We did fix this problem by applying a shim. Overall this vehicle is very poorly designed. They were in a hurry to push this vehicle out the market.
www.jpimportz.org

Thanks for your input. Is this a safety concern? Additionally when I push hard on the brakes something snaps back (like a two metal parts together) and the sound stops for a while.
Thanks

I bought a 2001 MDX before when it came out the first year. It has some minor squeaks and stuff. After that I thought I would never go for the first year car. Thats why I went for the second year Lexus, thinking that whey would have worked out the issues by now.

This is not a safety related problem. But It would upset me if I pay so much money on a new lexus and it has all kind of problems. This is the first year for the GX470. It will be a better car though. I love the way it ride.
www.jpimportz.org

Mine is a 2004 and I was hopeful that they would have worked out all the issues by now. I absolutely love the car when the sound is not there
Thanks for your pointer on this issue. The next time I go to the dealer (which will be soon) , I will point this to him. Will keep this forumm posted.

Hi guys, have a new gx with everything else but the kdss. The noise is probably associated with this NEW option which is located in the rear. I do not think they have had a chance to work out the bugs with this system yet! However I'm sure that you are not happy with a 50 g vehicle with this noise. This is a new option ! That's why I didn't get it! I would bet it is something simple. I'm loving my gx have had it three weeks. Have over 1.600 mi already. So far the best vehicle I've ever owned! Hope your problems can get resolved.