I looked through the forum threads and found info on strut bushings, brakes, wheel bearings etc. None of them seemed cover my situation.

I am feeling a vibration that starts around 42mph, persists in varying degrees up to about 65 then smooths out. At 80 I feel nothing.

Vibration is not in the steering wheel, rather it feels like a whole car vibration

I have had the tires rotated and balanced twice, balanced at two shops (dealer and tire store) and still the problem persists. Front control arms/ball joints are relatively new thanks to a couple of black-ice-in-the-corner incidents

Dealer mentioned something about bushings where the axles enter the center section when I asked them to look at it. I asked about driveshaft and u-joints but they kinda blew me off. There is no shimmy or shake, only a mild modulation when braking.. Relatively new rear brakes.

EDTA:
I apparently misunderstood the service rep. What they really meant was that the adjusting collar in the two piece drive shaft was worn out and could not be tightened any further. This was leading to looseness in the center bearing where the two pieces of the driveshaft come together.

I ended up finding this out from another shop. They ended up putting in a new drive shaft but that did not resolve the problem.

Car has 218K on it.

Is there a way to definitively identify suspect components to check out? Dealer wanted 2200 for the center section bushings they mentioned. Trying to decide if the investment is worthwhile.

Thanks for any thoughts.

 

Sounds like you have covered a lot of the bases. Drive shaft maybe if you are good or have a buddy you can do that work yourself. I had a bad vibration occur after i had new uca and ball joints done. Turned out to be the tires and cupped. Shop did the balance and didn't check for that because you couldn't see any wear pattern but when you spun them you could see the problem.

 

All these little rubber parts at this stage are high possibilities for change. The strut bar bushings front and rear are typical. Engine and tranny mounts as well. Carrier bushings, tie rod ends...
The investment in making it feel right is practical up to a point. Do the low cost fixes and decide if you want to put more $ into it relative to your life expectancy with the car.

 

we might give you a better "guess" if we knew what you were driving.....

also while it is vibrating, put your hand on the shift lever and see if you can feel anything..

 

These are all valid points of interest. Unfortunately there is no one thing that would cause it. There are lots of variables. Start with the cheap and easy and move up the latter. My suggestion is struts, they may not be bad but getting there....

 

Check for a bent rim, usually your not going to see it with the naked eye unless it's really bent, but even balancing and rotating it 10 times won't bring the road force within spec. I would be sticking with the wheels as those are the main focus when finding a vibration that is speed related.

 

Well billy I have a 93 with vibrations and I feel the shifter shaking at 45-60, what does this mean sir?

 

Thanks for all the suggestions, I certainly have something to think about..

Sorry I did not provide more detail about the car. One gets focused on what one wants to convey and forgets about some of the basics.

98 LS400
No shake in the shift lever
Wheels are LS430, not original to the car but several years old now. Will have to check for bent/damaged.
Struts could certainly be an issue, the car floats more than I remember on road swells. No leaks though.
Starting to get very mild exhaust noise, had rattling heat shields recently.

At the moment, I am putting 700 miles per week on the car more or less. When I get home I am not too interested in spending time underneath it. Nor am I interested in spending money week after week to have someone else replacing bits and pieces. I may have reached the point where a used LS430 is in my future.

I do appreciate the comments though, understanding the scope of the possible solutions helps a lot.

Blueman2

 

I agree with 3uzfte at that speed most of the time it is a tire or wheel issue.

 

get it up to speed and u said its at 42-65 mph correct,well get it to 60 mph and throw it in neutral,if it continues to do it then its not drivetrain related
never known a bent rim,or out of balance wheels to smooth out at higher speeds
dont start throwing parts at it
have the mounts checked
i believe there is a rubber thing in the drive shaft..a coupler sort of piece or maybe two..have them looked at as well
another thing to have looked at is ur rear axles

 

Blueman, have you had an alignment recently? I suffered with a serious highway speed vibration on my similar 2000 LS400 from about 75,000 to 85,000 miles - bad enough to cause the front passenger seat back to visibly shake. I had several shops road force balance the tires and look at the suspension with no solution.

It wasn't until I bought a new set of tires and had an alignment that it was discovered that the front wheels wouldn't hold an alignment and that the strut bar bushings were worn out. A new set of strut bars/bushings completely eliminated the vibration.

I've had less serious vibrations caused by out-of-balance tires and a defective tire that could not be road force balanced.

 

Just to update and close the thread, my issue turned out to be failed engine mounts and a very compressed tranny mount. Replaced all three and the issue disappeared.

Thanks for all suggestions and comments.

 

That'll do it. When my engine and trans mount were bad I had noticeable vibration at 45-65 ish mph. When put in neutral it would go away.

 

yep, engine and trans mounts, very common at this day and age of the car.

 

kudos for giving a conclusion to ur thread! most do not do that..moderators should have a way of tracking members who do follow up and putting something by ur name..would be an incentive for u and others who help. by giving a follow up it also helps people in the future who might have the same issues! thank you