TRM04

Well let me start from the beginning to help all you better understand the situation. I bought my 97 LS400 2.5 months ago with roughly 80k miles on it. Before the purchase on one of my test drives, I noticed that the car had a shuddering sensation coming on around 35-40mph. The owner wasn’t aware of it at the time…my theory on that is that he basically became immune to it since it probably gradually built up the shudder. Anyway, we both came to a temporary conclusion of that the car was in a desperate need of new tires. I went ahead and purchased it and about a month later bought 4 new Michelin tires hoping the shuddering would be concluded from this. Well, it wasn’t but it was drastically reduced. Occasionally it is rough and seldom it is not even noticeable. Within the next week I took the car to my local dealer for an evaluation of the problem. After a half day of having the car they were not able to reproduce it. Few weeks later I took it back again and told them that there IS A PROBLEM and that they need to take a longer test drive. Well this time they had me drive with the mechanic and the many times the shudder happened it was very low shuddering. They told me that whatever I was feeling (because they couldn’t feel it) was normal. Enough of that dealer... I took it to another one…to make a long story short…they couldn’t feel a thing either and said the car is normal.

Well, being just about fed up with my local dealers, I was ready to give up and probably put the car up for sale (and probably still will). I thought I make one last attempt to another near by dealer who claimed they had a diagnostic specialist on site who supposedly gives Lexus engineer’s assistance. I thought, why not, I only have to loose another $45 in diagnostic fees…

So here I go…off to the dealer with full intentions of walking away with the dealer telling everything is normal. I get in the car with the specialist and off we go for our test drive. Low and behold…he sees there is a problem. At this point I am totally baffled by his expertise and experience. During our 25 minute test drive, he did all types of tests to pin point the problem. He drove with the parking brake up to see if a caliper is locking up in the rear. He held the brake pedal down and accelerated the car both at a dead stop and while rolling to make sure the torque converter/lock up was working properly. He continued with many other road tests. Unfortunately, according to him, everything passed. With his 35+ years of professional knowledge, he was stumped for the first time. Never has he seen such a problem. He got me thinking twice of how knowledgeable and experienced he REALLY is. At this point, he wanted to keep the car for a day to call in a Lexus engineer who has access to many resources a dealer technician doesn’t have access to (i.e. resources at the Lexus factory and other engineers).

Here’s the latest. I called back today to get a status only to hear the worst… They don’t know what’s wrong. At this point not only does the specialist there have no idea, but its also stumped the engineer. They said they can continue to diagnose at my expense but it may not lead to anything. I told them no, I’ll be by to pick up the car.

I’ve read on this very board, people discuss vibration/shuddering issues on the LS400 many times and I have relayed the resolutions I have seen people find to all 3 dealers. Even with that information, no one can figure it out. The transmission fluid is brand new, the diff. fluid is about a week old. Tires have approx. 2000 miles on them. Someone please help. If I can’t find a solution soon, this car is going up for sale. This is my first Lexus and probably my last. Back to Acura’s I go…

Thank you for reading.

Ahad

///MDex

- Try new wheels; yours may be bent.

- Try new suspension componets; yours may be bent, ort worn out (bushings).

- Try new frame; oops, that won't work; you sure the frame isn't bent?

Does it get worse when you apply the brakes? Warped rotors.....

It only does it when the car is moving, right? So it's got to be one of those culprits. If it's only at certain speeds, I'd say it has to be the wheels that are out. Shoot, check the torque specs on the wheels as well; improperly torqued wheels (in perfect shape) can cause a shudder.

Just throwing out what seem obvious to me. HTH

RalAegidius

Maybe the lugnuts are improperly tightened???

Ral

wwest

Needle bearings in one of your driveline u-joints is in the process of failing, what you feel is the driveline "nutating" as if it were warped. Only happens when the bad needle bearings happens to come into the right (wrong?) positions.

RON430

Everything Dex said plus don't be surprised if a dealership isn't the repository of all automotive information. Try to find a good alignment/balance shop and see if they can either pin it down or eliminate some things. Swapping a complete set of wheels/tires seems worthwhile, if you can find them. Also see if they can tell you if the vehicle has had any serious repairs done to it. If you can eliminate all the easy to fix issues, then it gets harder and probably more expensive than it is worth. If you believe this is something generic to Lexus ( I don't) and are convinced that Acura is a better car, save the anguish and go get another Acura.

TRM04

paradox

This problem is not endemic to the Lexus, by any means. When I had my Jag, the same problem was caused by an improperly balanced steering rack. Wouldn't just cause feedback thru the steering wheel, it actually felt like the car was shuddering at times... On that rack, there's a screw used to adjust the rack once it's been removed. I don't know if it's applicable to the Lexus steering mechanism, but I'd look into it.
Upper control arm bushings, but this'd be easy to tell with the car on a lift. Also would make the car seem to have a tendency to wander.
Tranny mount possibly?
Let us know if there are any updates with this. Good luck!!

shamrock

sounds like a driveshaft / u-joint to me.

RON430

shamrock - Same thought occured to me but that is a very rare occurence especially on a LS with only around 80K. Of course that is out the window if there was a serious bash involved. Replacing a driveshaft might slip by on a repair after a big crash. Only thing that votes against the drive shaft is that the vibration would probably repeat as the transmission shifted and he says it is only around 35 or 40. He posts that the new tires helped a lot so I go back to Dex that maybe there is a bent rim. Strange.

Blue

Just thought I would give my 2 cents worth...Lincoln Mark 8's develop a shudder after transmission fluid change at 90+thousand miles. Feels sort of like you are running over the little hard "Turtle Shell shaped thingies" between lanes on the highway. Mine exhibited the trait when under moderate throttle at about 35 to 43 mph??? Seems the transmissions accumulate an amount of "Varnish" like stuff on the inner workings.
My mechanic told me "Torque Converter" at about $1400.00 but it just didn't seem that bad!?
Long story short...opps too late, I bought a $9.00 can of Transmission Mechanic in a Can. About one quart, put it in the tranny and the shudder went away in the next 200 miles. My German Step-brother told me he used the stuff in his GMC pickup at 135,000 miles. Neither of us needed a torque converter, and $9.00 is a pretty cheap trick. Lots of people laugh, but I sold the Lincoln, and it has another 25,000 miles on it now...Same tranny, no more shudder/stutter.

DevilDog

MY 2 cents, even though your problem is unique.

Motor and trans mounts.

ChrisK

iTrader: (1)

TRM04,

Can you tell me more about the trans fluid? Did you change it? What brand did you use? Did you change 2qts by draining the pan or did you flash all 8qts or so?

tn52

I concur with Dex and Wwest. Since you mentioned that the new tires drastically reduced the problem, it will be likely something have to do with tires/wheels. I suggest you check this out with the following steps (easiest first). If you pass one test, go to the next one:
1. Check for bad bushings: jack up the front tire on each side and check for play in the bushings - remember to check it by shaking it the 3D way
2. With the tire not touching the ground, manually turn it and watch for the roundness/trueness of your tire + wheel. You have to be very critical because our car is very sensitive to vibration even with a minor out of round problem - If you see any problem, swap this tire out with the back one (same side) and test drive. If you find a bad one, go to the tire store, tell them to take off the tire and find out if your wheel OR your tire is out of round.
3. It could be possible that your u-joints are at the border line to fail. If you also hear/feel some low freq humming & shuddering, then they are likely your problem. Otherwise, it's difficult to tell when they just start to go bad.
Good luck.

TRM04

The dealer did it. Whatever their standard procedure is I'm assuming...

TRM04

I thank you guys for your swift responses. I am actually going to swap wheels with a friend of mine tomorrow to eliminate that concern. That leads me to my question. Will the new SC430 18 inch wheels fit my 97 LS? We're just using them for our test. Maybe I'll take pics of the car with them on there to show you guys.

I'll keep all of you updated.

Thanks again...

Ahad