I have a 2003 LS430 with only 120,000 miles. For 2 years I have had a vibration in the steering wheel. The vibration is always there but the intensity varies. It can be hardly noticeable to so bad you can see the steering wheel shake, although slightly. It can be noticeable at 40mph to 75mph and seems to worsen the faster you go. It is not a shimmy but a vibration as if you can feel the road.
I have read everything on this site and applied most of the advice. It is not the wheels or tires. I have put 4 different sets of tires on with no change. I have had the tires/wheels computer balanced. I even had the wheels alone checked and they were perfect. I did have a shimmy in the steering wheel and replaced the lower control arm bushings and that fixed that. I had the brake rotors turned but they were almost perfect. I replaced the steering column bushing. As per this site I checked the steering column and it appears to be OK. I have had numerous mechanics and front end shops check the ball joints, wheel bearings, drive train, motor mounts, shocks, etc. and they are supposedly all OK.. I understand physical/visual inspections can't always detect a problem.
So, I'm not going to throw a few thousand dollars at this replacing everything. I've read about some on this site that have done that and still have the problem.
If anybody has any advice, thoughts or ideas it will be greatly appreciated!
Thank you,
Peter

 

Switch to stiffer lower control arm bushings (e.g. from ISF), original bushings are way too floaty.
Next thing i ll look is power steering fluid - see if you can replace it with fresh ATF of a good brand.
Next thing i would look at is front rotors.

There is nothing else that causes this vibrations (considering you havent installed chinese parts prior to vibrations)

Good luck!

 

For me the steering rack bushings is what solved my problem, though mine is about double your mileage so I don't know if your bushings would be that bad yet. The ball joints helped quite a bit as well, they seemed fine on mine but when I took them off to replace them you could spin the ball stud around with one finger, no resistance at all.

 

I replaced the lower control arm bushings with Lexus OEM parts, rotors were turned and were almost perfect and I changed the PS fluid a few months ago. That did seem to help then. Do you think I should replace it again. Maybe there is a flushing process that needs to take place over time?

 

Check the rack and all ball joints, they can feel fine from below and with a 3ft bar and still deflect on road

 

has the driveshaft bushings/bearings been checked? Maybe its possible a weight fell off the driveshaft or it has a dent or something , did anything go under the car on the highway or anything like that?

 

Engine Mounts?

 

I would also recommend looking into the motor mounts. I have a vibration/grinding kind of noise and I can hear and feel it in the road on my 460. This happened right after I changed the starter which requires me to remove the exhaust manifold, Y-pipe, some suspension components and lift the engine to remove the passenger side mount so I could have clearance to remove the manifold. I put everything back together and had this vibration/grinding noise. I used a so vac to determine that the flange was leaking and I could not be sure the manifold was also not the culprit since I tried the gasket. Needles to say I ordered a new manifold gasket and to everything back apart, I also got new nuts and bolts. I tightened everything back up and eliminated the leak but the sound was still there. Upon closer inspection I noticed the driver side mount has some dried up fluid on it and can only surmise that it leaked all the fluid out and is now bad. Another sign was that my car is way lower on the front driver side which I thought might be the air suspension but after checking techstream and doing some adjustments that was not the case. I ordered 2 OEM mounts and they should arrive this weekend. I'll probably get it done next week when I'm off a couple of days.

At low speed I can barely hear or feel it but when I'm on the highway is loud to the point that I think the engine is toast. Just because your mounts look good don't mean that they are good. There is no way way to determine it except to tell the engine and see how much it's lifting up inside the engine bay.

 

Did you end up solving your vibration?

 

Tranny mounts?