High speed vibration ls400
 

As the title says my 1991 ls400 is vibrating at high speeds (100+), and then go away for 20 min or so. I've recently done new brake and checked the ball joints. Is this a common issue? Any information I could get on this issue is greatly appreciated.

That doesnt make a lot of sense. Balance your wheels on a hunter roadforce gsp9700 machine. Do you feel it in the steering wheel or seat?

It's in the steering wheel, I've done the tires too thinking it was a broken belt

Does that mean you drive at 100+ for more then 20 minutes? :p NICE. I used to drive like that, when I was in my 20s. I had an 88 Regal, the digital dash only read 128, but it went a hella lot faster. (about 4 hrs through Maine)
Anyway, is it a vibration or a shake? Vibration is usually drivetrain related, (engine to rear axle) a shake is usually tire and suspension.

Vibration can be caused by a number of things. Improperly balanced tires, warped rotors, ball joints, bushings, motor mounts, and (most often overlooked on the older cars) driveshaft bushings/bearings. I noticed that you have addressed some of these issues already. Wheel balance CAN give some of the symptoms you indicated, so start with that first. On my 92, I eliminated just about everything that could possibly be creating the problem, and yet it still existed. I recently had my motor mounts changed(front and rear) as well as had a replacement driveshaft bushing installed (temp one,, still have to order a new one as mine was completely shot) and the world of difference it made was immesurable. Since you have balanced the tires, and done new brakes,,have the rotors checked for warpage, and also make sure that you use a Hunter roadforce machine to balance your tires. Lexus' are VERY sensitive to balance issues period, and it can be a pain trying to track down a vibration, knowing that you have done certain things already.

Ok, I have exactly the same problem. Vibration after I reach 100mph, like I drive on bad, rough surface. I didn't know that we have Hunter GSP balancers in Czech Republic, but we do, so I will get my wheels balance on this machine and I order some suspension stuff on my car. Strut rod bushings, drive shaft bushing and new rotors plus pads. Will see what will happened and let you know.

Same issue I had with my 96 LS.

I replaced inner/outer tie rods, ball joints, strut rods, well everything on the front suspension. To keep it short.

It's difficult to find strut rod bushings. And the whole part is expensive. Look for bushings here.
http://eepauto.com/

This made it drive like new and no vibration at any speed.

Here, they have it.Straight from Emirates:D
http://www.ebay.com/itm/4867440051-G...53.m2749.l2649