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2007 GS with active suspension - what is causing the nasty rear end clunk?

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Old 11-20-12, 11:58 AM   #1
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Default 2007 GS with active suspension - what is causing the nasty rear end clunk?

My 2007 GS-450h is at Lexus for the second time for diagnosis and in warranty repairs for a rear end clunk. So far however, they have not found anything wrong with my car this time either. Both times a "super tech" has ridden with me and experienced this clunk on a test drive and agreed that something was indeed wrong and should be fixed. But then they have commented that the shocks look fine, no leakage, blah, blah, blah... Actually, the first time they aired my tires up to 44 psi and the problem did get way better, but everyone says too that this is too high a pressure to run all the time.

If anyone has some thoughts regarding what could be the cause of the following symptoms, please reply!

- When I go over a 2" sunken manhole cover in a flat road at about 40 mph, the right rear makes a nasty clunk; it is the sound that a suspension would make if it had "bottomed out" (clearly the suspension is not bottoming out, I'm just trying to accurately describe the type of clunking noise that is occurring)
- hitting bumps, speed bumps, etc. NEVER makes this noise; it seems that the clunk is related to when the suspension needs to extend, not just compress
- right rear has also clunked before when braking hard and turning right into a parking lot driveway
- left rear has never made this same sound

Thoughts and other comments:
- My GS has the active suspension which includes some kind of active element in the middle of the rear sway bar
- Car came with run-flats, but currently has normal high-performance summer tires on it
- Maybe the right rear strut is "topping out" due to an internal problem with the strut itself (bad rubber bumper, etc.)
- Some other models of Lexus have received updated (thicker) sway bar rubber bushings to help with various clunk noises (F-Sport front anti-sway bar support bushings)

Thanks in advance!

Last edited by JShort; 11-21-12 at 02:15 PM.
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Old 11-20-12, 12:10 PM   #2
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Old 11-20-12, 02:08 PM   #3
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loose stuff in the trunk maybe
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Old 11-20-12, 02:11 PM   #4
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your tires are fine and that is way to much pressure.

the sway bar bushings where for the F-Sport, do you have these on your car?

are you fully OEM suspension or do you have lowering springs?

with your symptoms are you driving slow or fast? how about going slow down a really rough road? I had something similar to what your explaining and it would only happen while going slow. Normal speeds I never heard anything. Slow down a rough road sounded like it was going to fall apart. Mine turned out to be the control arm bushings.

to me it almost sounds like it could be your end links or a bushing.

lol have the tech ride in your trunk, battery will keep them warm, and see where the noise is coming from.
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Old 11-20-12, 02:32 PM   #5
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Check the rear swaybar linkage. Had one rust right out on a ford, my first car, back in the day and it did exactly that. It was like a $15 part and I replaced it myself easily.
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Old 11-20-12, 09:35 PM   #6
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Do you have **** (Active Stablizer Suspension System) or AVS (Adaptive Variable Suspension) The clunk noise could be sway bar linkage as BinarJay stated, maybe you should try on turns and see if you hear the noise, I would think you would hear it then.

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Old 12-12-12, 07:52 PM   #7
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I had a similar issue with my 06 GS430. I took it to the dealer, and they found that the noise is coming from the rear brake calipers. It was still under warranty, replaced for free and the noise went away....

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Old 12-26-12, 04:44 PM   #8
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The cause for the rear end clunk has been resolved!!!

And, thank you to everyone that responded! It sure does sound like similar clunks have been caused by different things.

The third time to the dealer was the charm. They replaced the right rear strut (extended warranty) and the active sway bar battery (my cost) and my car sounds like a Lexus again.
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Old 12-26-12, 05:14 PM   #9
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You know what would be a cool idea, is to mount one of those gopro camera's in that area. I do not see why mechanics do not use them.

I would go through the rear suspension and see if anything is loose first, then check bushings. But, to me it sounds like the shock is blown, I would take it apart and exam it.
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