Trouble Shooting Vibrations - Any Check Lists?

[ebridges]

Lot's of good threads on various solutions to solve vibration problems especially in the Gen I LS400. I've tried several and its getting expensive.

Purchased my 91 LS400 13 months ago with only 70,000 miles, two owners and excellent records. From the day I picked it up in TX and drove to Atlanta, I've been plagued with high speed vibrations. Today I have over 105,000 miles so I've put on 35,000 miles in just over a year. I love this car. Also own a Gen II LS400 1996 with over 192,000 miles. There isn't any comparison in the two "rides".

Immediately upon getting home, I bought both a lifetime balancing and lifetime alignment package from Firestone. The alignment (4 wheel) has been done three times and the 4th will be tomorrow. It was never obviously any problem.

However the tires (Michleins, H rated) which came with the car, were never balanced satisfactorily after 6 or 7 attempts.

Firestone did discover a bent right rear wheel, which I had repaired at a local speciality shop for $90. It's been fine to date. They also pointed out the split rubber boot on the same wheel.

So, shopping for new tires. Ended up with Toyos Proxes from a local chain, Kaufmanns. I liked the performance of the new V rated tires and the price was just over $100/tire with 65,000 mi warranty.

BUT again, unable to get them smoothed out at the 75-85 (cruising) range. The tire dealer balanced them about 7 or 8 times, with four different technicians. Still a whole car vibration starting just over 70 up to 90. Often after "throwing off" one or all of the weights. (of course they tried stick ons too, but still vibration)

I tried the "sand pebbles" auto balancing inside the tires next. NO HELP. (You can see my "desperation"). :chairshot:

So went to another local tire and brake specialist who removed the "sand pebbles" and did a pretty good balancing job, but the weights left within 10 miles. Back to them, and the other tech/manager, made them stay on. Still the same vibration.

I have OEM chrome alloy wheels - original equipment. I've learned a lot about FN(S) weights and found two folks who could make them stick on, by bending the clips properly.

Okay, changed the tranny mount - easy. No help.

Changed the motor mounts - not easy. But at idle, cannot feel the motor at all. BTW, the old mounts did not appear all that worn. Still the whole car vibration at 80. Very annoying.

Next, found a great shop - which is family owned for over 35 yrs, and they did tire truing and spin (on-car) balancing. I watched and asked lots of question and the weights stayed on. But, still a vibration.

Now over 15,000 on these new tires.

Here's a hint, I think. The vibration seems to be somewhat intermittent. It will "smooth out" acceptably for a mile or so, then get rough again. Doesn't appear to have anything to do with the load, uphill or down. In fact, I put it in neutral and coast downhill at 80 - 85 and the vibration doesn't change.

The right rear axle boot is split and it may be getting quite dry. Discovered the split at the very first balancing job, Went to a Lexus specialist place and they suggested just ignoring it, which I did.

I know that a lot of things "could be" the culprit but don't believe that I can afford changing everything that "might be" the problem. i.e., drive shafts, axles, u-joints, bushings, ball joints, shocks, differential mounts, etc.

I think I've eliminated the motor and transmission as causes - no change while coasting in neutral. The fact that it is not consistant, leads me to suspect it has something to do with harmonic vibrations between left and right side components. (It's smooth as my 96 LS at 60mph.) But a rough ride at cruising speeds, which is most of my driving.

Next step is to acquire the 10mm Hex to check the torque at 61 ft lbs on the axles.

QUESTION:

How would a Professional, (JP1 ?) go about checking out the the cause? There has got to be a "decision tree" type of procedure. Anybody have one or seen one?

Thanks for reading this far And thanks for any tips.

[90LS400Lexus]

My car did (does) this and it is the tires. I took it to shop after shop. None of them could find anything wrong. I finally took it to the local Lexus dealership to see if they could figure it out. Seems as if the tire is "cupped" because the car was not re-aligned when I had new rear struts installed. It makes sense because the vibrations did not start until after about 1000 miles. They said I should "wear" these tires out and have it aligned and new tires installed, because since the tires are already damaged, it would not stop the vibration -(just the re-alignment). Sometimes it does it- sometimes it don't - it all depends upon the temperature and road condition.

Since you have already had your tires checked, this may not be your problem.

Sounds like you have replaced all of the items that normally cause vibrations.

Good luck.

[nc211]

90LS400, was curious, did you ever fix the tires on this old thread?

[mehullica]

Have you checked the driveshaft?

[maxed_out]

Can anybody PLEASE check TSB's on this item. I'm chasing the same issue. My parts guy at the dealership says once in a while the driveshaft hanger bearing can do this.

He has seen them also replace bushings in the rear. I really think my vib is from inside the differential like a bad bearing or bushing. If I run the car on jacks, I get a lot of drivetrain vibration-but its different feel than the "on the road" vibration.

[larry2]

Had vibration issue with my '93 since I bought it '97 - occurred around 100-110kmh and worse when under load . It had 115000km on then. I took it to the Lexus dealer. He balanced wheels - did not fix it. I asked them to swap wheels with a demonstrator to rule out wheels/tires altogether, just to try it. They refused but decided it was the driveshaft - it got replaced, Lexus coughed up 50% of replacement. It somewhat fixed it, but came back shortly afterwards. Years went by - I just tried to keep it over 120. Replacement tires did not help. Second set of replacement tires at new dealership in another city with full alignment - 90% fixed, at least for a few thousand kms. Problem is back again although not as bad, but now at 115 - 125ish. It seems quite variable and hard to describe - some days worse than others.

The car now has over 300km and is still a lovely jubbly cruise ship. I've considered new replacement C class Benz or G35 but test drive disappointing - no replacement for the silky LS. By the way my car is called Larry. I bought a Land Rover Disco couple of years back too, but could not part with Larry.

These cars seem to have a definite and strange susceptibility to vibration. Can some informed Lexus mechanic gives us the full goods on this so we can get it fixed and enjoy them to the full, please ?

[SKperformance]

Has anyone changed the brake rotors?

Had a high end balancer not a normal shop check the wheels?

[larry2]

Has anyone changed the brake rotors?

Had a high end balancer not a normal shop check the wheels?

←

Brake rotors have been replaced twice. All the work on the vehicle has been done by the Lexus dealer except oil changes.

[monarch]

My '91 LS400 with alloy wheels had a mild vibration problem too at 60-65 MPH. New tires and balancing didn't cure it. Then I bought a used set of standard, non alloy LS400 wheels. Now car is a smooth as silk - but doesn't look as nice with the standard wheels.

[pachocco1]

I think your wheels are at fault as well. That repaired wheel, I would scrutinize the trueness of the repair. Have you try swapping it out with the spare to check for any difference? or moving it to another location to detect any change in vibration source?

[bartkat]

Drive shaft I'll bet. Can be balanced by attaching a radiator hose clamp, then test, and move the clamp around until the vibration is minmized. The screw of the clamp acts as a weight. Had this done on a coupld of vehicles and it worked.