I recently bought a CPO 2007 GX 470 with 110k miles. At no charge dealer made repairs re the Bulletin about clunk in rear when I slowly drive over speed bumps. Had all front and rear shocks raced with OEM shocks, and four new Michellin MS2 tires installed. Rear end still feels like is is bottoming out sometimes during regular local and freeway driving when going over different times of road bumps. My 'i89 a Dodge Ramdharger ( only car I ever bought brand new off the lot ) with 174k miles and old shocks and original springs drives better over bumps and speed bumps than the GX. One Lexus dealer said the reason is because the rear air bags ( that are not leaking )do not fill up fast enough when going move bumps and that can cause the bottoming out feeling. My mechanic is going to check it over again. Any idea hat could be causing the bottoming out feeling? Thanks

 

Mechanics we drove the car today and felt the same what feels like minor bottoming out when going slowly over speed bumps. Car was at normal height and comfort control was set in middle of dial. Then he changed height to high in rear and when we went over speed bumps there was no noise or slight thud, felt like the front suspension felt which is normal. He's going to put it on rack to see if he can see anything wrong with the rear suspension; just had new rear shocks installed.

 

Sounds like the rear air bags. They could be leaking or they could be set wrong.

 

Have him measure the ride height when it's in Normal. The sensors might be out of adjustment.

Chip H.

 

I replaced my rear air bags/springs and shocks and still have the problem, not always, but most of the time. I can temporarily solve the issue by cycling the ride height, but it always returns to a lower position. My right rear sits noticeably lower too and that is where it feels like most of the bottoming out is occurring. The ride height needs to come up. As mentioned the dealer can read the height sensors via their computer and reset them if they are still functioning properly. Ask your dealer to hook it up to their computer and check them.

Adjustments can be made to the leveling arm mechanism, but if one or both of the ride height sensors are not functioning properly it will only provide temporary relief.

 

My airbags are still intact, no leaks yet. Rear shocks are original. Depending on how sharp the bumps I hit are, I may get a thump/thud in the rear. Can't seem to replicate with every bump. Frustrating.

 

The mechanic and I drove slow over speed bumps with the rear raised and could not replicate the symptoms;the rear went over the bumps as comfortable as the front does. However when we changed the height setting to normal, the after-effect sound could again sometimes be heard and felt in the rear. I'm planning to take it in to the Lexus Dealer to have them check to make sure the sensors are working correctly. Has anyone ever heard the the rear bags are small and do not fill fast enough to be able to prevent the symptoms the car has? One Lexus dealer said that is the reason, but another Lexus dealer said they never heard that before. I don't want to drive the car in the raised rear height position when having to go over speed bumps, and would rather just "crawl" in slow motion over them if necessary , but I not sure if this is the way the vehicle was designed for drivers to have to drive them. Thank you all again for your comments; they are very helpful.