Bought an 06 a few months ago and have been refreshing the car slowly to try to eliminate highway vibration.

Done so far:
- lower control arm bushings
- rotors/pads
- struts/springs
- new wheels/tires

What should I try next? I will say every fix above has helped. I still get some steering wheel and booty vibration in the 75-90mph range.

 

Steering rack bushings might be bad, allowing vibrations to get to the wheel.

 

Not necessarily comprehensive and in no particular order:
Steering wheel-
Low PS* fluid
Tie rods and/or ball joints (upper and/or lower)
Which lower control arm bushings were replaced? Front lower control arms have a front and rear busing.
Did you also replace the strut mounts?


Booty-
Driveshaft bearing and/or guibo.
Any of the 3 engine mounts, 2 under the engine and 1 under the transmission.
Numerous bushings in rear suspension components.
Over time a combination of bushing wear and sagging springs can allow the rear wheel camber to move permanently outside alignment specs.

Always use quality parts preferably genuine Toyota/Lexus if possible. Cheap parts, especially suspension related, will feel great for about 6 months.
I'm sure I've left something out...

* LS400's and 430's use Dexron ATF as power steering fluid

 

Will take a look at these, thanks! FWIW I have 90k miles on the boat.

Replaced the front lower control arm rear bushings. Strut mounts were replaced. Springs were also replaced.

One thing to add - not sure if it helps with diagnosis - vibrations get a bit worse at the end of long drives. Did a 300 mile drive not too long ago and the ride quality deteriorated a bit at the end. Was back to "normal" the next day.

Anyone else have ideas/suggestions?

 

^ That is good information. I was thinking maybe your tires or wheels were out of balance (even though you replaced them) and have a resonance vibration at high speed, but the fact that the vibrations progressively got worse over 300 miles would seem to eliminate that possibility. Are you getting any noise - or just vibrations? Did you check the fluid level in the pumpkin? Its a pretty easy DIY to do a fluid change of the differential fluid, there is a thread on that and I just did that service.

 

No noise. I'll track down the thread you mentioned and add that to my list of things to do.

I'm thinking of doing the engine mounts as a first try since i get the occasional rough 2nd to 1st down shift when creeping up hills at low speeds. Will check the PS fluid too since that seems easy (I think?). Not sure if this makes sense.

 

There are many threads on here for the "rough 2 to 1 downshift" problem, eg. https://www.clublexus.com/forums/ls-...own-shift.html

Solution is to send ECU to SIA Electroncs and it fixes the problem. This is not going to fix your high speed vibration issues. While you are thinking about your transmission you might want to do a set of 3 drain and fills of the transmission fluid if you are still on the original factory fluid. Sorry to pile on maintenance items for you to think about. LOL

 

I know I say this a lot but def look into the rear engine (aka transmission) mount first. Not only is it much cheaper than the front 2, it's WAY easier to replace and often cures vibration issues without the headache of replacing the other 2.

 

Thanks, will do. I like cheaper haha

 

Motor and transmission mounts are one of those instances where Toyota/Lexus parts are pretty much mandatory. The aftermarket versions are not liquid-filled like the genuine part.

 

What you've described here, the deteriorating ride quality but then "back to normal the next day" is similar to what I've been experiencing with my LS. This comes AFTER having checked the front brakes, swapping out the old tires, and replacing the Front Upper control arms. Next up, I guess, would have to be the Front Lower control arms?