From a member, concerning a repair experience with his Lexus 2011 RX450h:
The problem is a squeaky rear end when going over speed bumps or driving on uneven road surfaces. It started around 25K miles and appears to finally be resolved at 33K miles and 4 trips to the Lexus service department.
On the first visit to the dealer, they said that this was common and they lubed the rear end but did not go into specifics. This resolved the problem for a few days but then the squeaking started again. It is very annoying as we live in a development with several speed bumps so I get to hear this noise every day!
On the second visit to the dealer they had the car for three days and could not find anything wrong and said there was no noise when they road tested it over speed bumps and many conditions and only had normal noise expected from this model.
On the third visit, I did not make an appointment. I found a location directly across the street from the dealer that had a speed bump and asked the service manager to go for a ride with me. Three trips over the speed bump with the annoying squeak each time so I was told to make an appointment and he would enter this in the computer.
So I made the appointment a few weeks later and got a call that they had to keep the car for 2 days until new shocks came in. I asked them to road test it before and after the shocks were installed on the speed bump across the street and they agreed.
I also said that I thought the shocks were fine and that from everything I read about similar issues on the internet [including a report on TrueDelta], I felt it was the rear trailing arm bushings. That was quickly dismissed as not the issue and told that they were the experts.
I got a call that the shocks were installed and it was fixed. I picked up the car and immediately went to the speed bump across the street and of course it was just as bad as ever so back to the dealer immediately and asked for the service manger to take a ride with me. He sent the mechanic that worked on the shocks and as soon as we went over the speed bump he heard the noise.
I again suggested the bushings and then he said that yes they have a problem with them and said he could test it quickly. So out with the WD-40 and spraying the bushings and back over the speed bump, this time no noise!
They finally ordered the new bushings like I suggested on the previous visit which took about a week. The new bushings have now been installed and the car is like new, no more squeaking and it has been a few months now.