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90LS400Lexus

Odd Vibration- Possible Transmission Problem?

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After all of this talk about my "perfect" transmission- I may have a problem. The problem I am about to describe about my Lexus has happened three times- once last week and twice today.

Today I was driving on the parkway at a steady speed of about 45-50 mph- the car was in 4th gear and the lock-up was activated. I pressed the accelerator to gain speed to go around a slow car and while it was upshifting- there was a very quick vibration sound immedietly after it kicked in out of the lock-up mode. The sound lasted for only a second. The sound was virtually identical to running over one of those white "wake up" strips on the road at intersections, but there was none there where this happened. I tried to duplicate the problem and it did it again. I tried it a few more times and it did not do it. Last week- it only happened once- again, while accelerating and the car upshifting- as if I had hit a wake-up strip, or a imperfection in the road like the trackloaders cause. Does anyone have any clue as to what this could be? My transmission? Differential? Other than this- my transmission operates fine. The shifts are very smooth and no slippage. Any information appreciated.

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90LS,

I assume you where changing lanes to get around the car, and therefore were "turning" somewhat as accelerating. Is this the exact moment the car had the vibration?

In other words when you tried to duplicate and could not - where you just going dead straight?

first things first,, check the lugnuts on all four wheels 76 ft. lbs each!

99

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Thanks 99. The first time it did it - I was on a 2-lane and was going up a grade, when I pressed the pedal and it had that quick vibration. Today- I was just starting to change lanes, as I accelerated when it did it. When I duplicated the problem for the 2nd time- I was going completely straight. I could not get it to do it again. Now my car does have that slight rumbling vibration at speeds between 50-60 mph at times. Could this be linked? I will check the wheel nuts too. Thanks.

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Well,

The last EASY fix I can think of - is the tires and Balance issue. Others have always said the LS is pretty sensitive to tire balance.

Otherwise, one of the REAR CARRIER BUSHINGS could be checked. I think there's a current thread on this - from jzz30!

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I had what I think is a similar noise/vibration in a GM lock-up trans in my 94 Camaro. As the torque convertor clutch released, it caused a vibration, like the clutch shudder in a manual trans car. This was during the release, not lock-up. Eventually the whole trans was overhauled and the convertor repaired. It only did it about 3 times.

It is hard to tell from this distance, but you may be able to get a good trans tech to ride in the car with you to hear and feel the vibration.

It is something that can be caused by the wrong trans fluid. I have heard that Dexron fluids will cause harsh shifting in these transmissions, so perhaps a fluid change will be enough.

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Yes SRK- that is a common problem on the GM transmissions of the 80s and early 90s. Actually- my 92 Buick also has a "shudder" at times while in overdrive, but the symptom with my Lexus acts differently. The car has new tires, but I guess it is possible that it is out of balance, but I do not see how this can cause that "road strip" sound for about a second just as the accelerator is pressed. I hope this is nothing major. Thanks again.

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Well- I drove the car again today and it is still doing it. I have noticed that when I gradually accelerate and it kicks out of lock-up and out of overdrive- it does not do it. It only does it when I press the accelerator about 1/2 way down quickly. That explains why I have never noticed it before, as I usually drive my car very gently and have never had to kick it out of overdrive quickly before. It has a quick "rumbling" vibration until what I think is out of overdrive. I guess I will have to take it to the transmission shop. Seems as if the torque converter causing it. Its strange that no one else has seemed of have had this problem.

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Hi, My 91 LS400 does the exact same thing! It is just like running over the wake-up strips.

Tomorrow I'm going to change the trans fluid. Mine does it on gentle acceleration at highway speeds.

I'll let you know what happens. Hope I don't need a transmission.

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Hi, My 91 LS400 does the exact same thing! It is just like running over the wake-up strips.

Tomorrow I'm going to change the trans fluid. Mine does it on gentle acceleration at highway speeds.

I'll let you know what happens. Hope I don't need a transmission.

Thanks Frank. How many miles does your car have? My car does not do it on gentle acceleration- if I gradually press down the accelerator to make it shift out of overdrive. Only when I press it down about 1/2 way when it is to quickly shift out of overdrive is when it does it. I have planned on taking my car to the transmission shop tomorrow and let them look at it and see what they say. Hopefully it is something as simple as a fluid change, but I dont know. It seems to me more like torque converter problems. I rarely ever make the car shift like that and it may never do it again- as easy as I drive it, but I would like to know if it is something that will get worse and cost big $$$$ to repair. Let me know what happens. I will post what the transmission shop says tomorrow as well.

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My 91 LS400 has 200k on it. just turned yesterday.

I changed the tranny fluid today, I'll let you know tomorrow how it went.

Mine does it only on light accel, if I punch it, it by-passes the shudder.

My Mom's 90 LS400 has about 212k on it, I don't think she has experienced it.

Good luck, keep in touch

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Thanks. I tried to get it to do it again today and it would not do it again. I tried several times. Not complaining about that though. :) Someone on ClubLexus said that my problem sounded more like a differential problem, or u-joints rather than the transmission. I guess I will keep driving my car and hope it never does it again. I still need to have that differential checked, as they may be my slight, steady vibration problem at speeds of 45-60 at times. Good luck with your car. Keep us posted.

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Ahh! you're having the same problem I've been having for quite sometime. It's whenever the car shifts weight from one side to another, and it sounds like it's rubbing against the tires. At first I thought it was my shocks since my LS sags down so much, but I believe it wouldn't be an issue if we had the air suspension.

You can avoid it by not letting the car overshift when you're coming out of a quick turn or sudden lane change. Do it slowly, so that the car shifts to 0degrees instead of -1+.

It is possible the U-joint, differential, or the bushings might be the issue since I haven't changed those parts in the past few years. I haven't been able to check out the problem myself because I've been busy, but rest assure, it's not something you should loose sleep over. I've had the problem for about 5years, and nothing major has happened to my car. This spring, I'm going to attempt to isolate the problem. I'll post something then.

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Hello I have a ' 91 LS 400

It been doing the same vibration from the rear end of the car. like the others that I've read. When I drove it on any pave roads at any speed in high gear. Whenever I want to accelerate it seems that as it kicks down to the next gear it makes that vibration just for a momnent (1-3 seconds). In a day of lots of driving I get about at the most 5 respones for the backend. First thought came to mind was the driveshaft. It started to occur Dec. '03. If you agree or disagree that's fine. Just want to hear your response. Second thought, was the tranny. It seems fine and shifts great like it should. Next thought, check the records when the tranny fluid needs to be change. When I check it. It does need to be change. It shows a moderate color. Not to bad. Second owner of this LS. I wanted to convert tranny fluids over to synthetic oils. So instead of power flushing the system. I flush it by draining the pan. Which it hold 2qts. I use valvoline. This flushing method works well. I've been told that power flushing the system doesn't clear up the converter to make it fresh. It does clear up your coolant pretty good. I wait a week then drain the pan again. I did that for 8qts worth. 4 weeks total. I got one more week to finish the process. Once it done. I go ahead to convert over to synthetic. So far in about 3 weeks this LS has no problems with the vibration. I let you know if it does again. The longest time when it returns is a month an 1/2. Thanks for your time.

Paul

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I don't know. It may very well be a transmission problem, since you replaced the fluid. For me, I haven't changed the AFT fluid since I bought the car from my dad five years ago, and for an entire 6months it didn't rumble. I'm pulling towards the differential

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Thanks for the additional information. I drove my car again today and it did it once. As mentioned- it only does it when I rapidly accelerate out of "overdrive". It is actually almost like a "grinding" sound, or a "vvverrrrt" sound. The transmission shifts perfectly and smooth. Even when it makes that noise- it shifts quickly and smooth. There is actually not even a vibration when that sound occurs on my car. Its only the sound. The vibration is at steady acceleration at speeds between 40-60 mph. My car has nearly new tires and I do not think that is the culprit. It seems to be getting worse and doing it at more speeds. ASAP I am going to try to find a repair shop that may know about differentials, driveshafts. It is really discouraging as I bought this car thinking that it was in perfect working order amd hoping it would be that way for at least a few thousand miles. I did have the rear struts replaced a few weeks ago. I do not remember it doing it that bad before the replacement, but I think it was faintly doing it. I do not want to put a lot of $$$$ in this car now, as I think I may have paid a little too much for it anyway when I bought it 3 months ago ($4000 + tax, then $200 for new rear struts). If it is going to be a high dollar repair- I will probably let it go and search for a newer (93+) LS400- or a Mercedes 560SEL. I have been thinking of a brand new 2004 Accord LX sedan, but I think $22000 is a little too much for an Accord. Even a base Accord DX is just under $20000. Some of the 2004 Accord EX with the navigation system can sticker for over $30000. :rolleyes:

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The problem you describe is a very common one with these cars. Mine had the same "rumble strip" vibration when coming out of Overdrive lockup when I first got it. It indicates that the ATF has broken down and is not lubricating correctly. A simple drain and replacement of the transmission fluid in the pan with Toyota T4 ATF did the trick. That's supposed to be done very 25K miles on my car and only gets 2 or 3 of the total of 14 quarts. If your tranny is fairly old, it might not hurt to get a complete flush/refill. That costs around $200.00 around here, but almost half of that is the Toyota T4 fluid itself and its nice knowing the fluid is fresh. Try just the drain/replace of the fluid in the pan first if you like. It worked fine for me and my understanding is that this symptom does not indicate that any permanent damage has been done to the tranny...thank heavens!

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That's supposed to be done very 25K miles on my car and only gets 2 or 3 of the total of 14 quarts. 

The transmission, torque converter, cooler and lines hold 8 QTS of ATF ... not 14!! You'll need to drain and fill the pan 5 or 6 times if you want to reduce the amount of old fluid to less than 10%!

:)

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Thanks for the reply. I will try to get that changed ASAP. Did you car also have a vibration between 40-60 mph? I am thinking that problem with my car is something else. I am going to have the alignment checked, as some have said that was the problem. Thanks again.

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Thanks. I actually took the car to the local Lexus dealer today for a oil change. They said that the transmission fluid was very dirty and highly recommended a change. They also said that my "v-belt" was cracked and also recommended a change of that. They quoted me a price of $56.95 for the transmission service - (whatever that all consists of - change of fluid in pan and filter ?) and $39 parts for the belt change and $76.00 labor. I am going to check prices elsewhere for these things.

I had an appointment for 3:00 for the oil change. I dropped the car off and walked over to their Toyota dealership and looked at the cars over there- particulary the 4-Runners, as I am considering the purchase of a 1996-1998 4-Runner. I went back to the Lexus service waiting room about 30 minutes later- only to discover that the car was still setting at the same spot. As I entered- they quickly announced to me that they was taking the car back at that time. The initial change only took about 20 minutes. They could have at least offered me a loaner car. They must not do that at my local dealer, as I always see people just waiting in the waiting room, unless they have no where to go. :D I will probably just take the car to a closer Toyota dealership, rather that the Lexus-Toyota dealership that is 25 miles away. My local Lexus dealership has the same service dept as the Toyota dealership. Probably a lot cheaper as well.

Thanks again for the replies.

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I have posted other replies throughout the forums about my problem on other folks' vibration problems. We have discussed that it may be tires, but it seem like it is something with the actual car causing it. I drove the car today and it was not doing it nearly as bad as before. It was near 70 degrees here today, so it seems like the warmer it is outside- the less it does it. Does anyone have any additional ideas, based on this observation?

I am guessing motor mount. Reason why- when I first start the car of the mornings, when the car is idling at about 1500 rpm, and the engine is cold, every few seconds- it will have a "out of balance" feeling throughout the car.- every second or so, as if something it out of round on the engine. Could this be a sign of a bad motor mount? If so, I was thinking this could be my vibration problem at 35-65 mph speeds. I know on the older cars- to check the engine mounts, you could open the hood, place the car in gear and press on the gas a little to see if the engine moves excessively, or if you felt a "clunk" from the engine compartment, that could be it (motor mounts). Any other ways of checking hte mounts on these cars? What is the sign of a bad transmission mount? Thanks.

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I experience my vibrations during summer, and sometimes during winter.

I don't think the motor mounts need to be replaced, unless you're experiencing a loud noise and vibrations during gear'd-idle.

Since there are people who have noticed this problem with their GM Cars and Trucks, and since Toyota used many GM parts and design (body-on-frame) to build the Gen 1 LS, I'm leaning towards a replicated flaw with the design.

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I was hoping it was a good chance it was the motor mounts, so I can put an end to this annoyance. What in the world would cause the engine to have that "out of round/balance" vibration at 1500 rpm when it is cold? After it warms- that goes away, but I still have that vibration on that seems to be mostly on acceleration.

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I have followed the mount path. (tranny and engine)

It lead me to the tires. Replaced.

which lead to the wheels. straightened. 2 were bent.

Which lead me to the differential. Replaced.

...knucklebushings...

...driveshaft...

...differential mounts(3)...

...rear sub-assembly mounts...

So I am running out of options here.

Points of interest.

Temperature sensitive also!

On a rack, the vibration seems to come from the diff.

I have put a little peice of wood between the diff and the car frame. it reduce

the vibration significantly.

There is one side mounted diff bushing and two vertical mounted bushing holding the diff. You can see them from behind the car. I had these replaced recently and it also reduced the overall vibration. But it is still there none the less. When examining the left vert. bushing, I notice that it has a slightly different form to it. Two 1/2 inch indentions in it appear at opposite sides. The other side appears to be a solid rubber mount. With a long screwdriver, I pried at the center bolts of both mounts. The right solid one did not move much at all with a good degree of force. The left one however, moves very easily, but only in the direction of the indentations (pressed in at north -south).

There are numbers on the side of the mounts. It starts with a

6 - 0 - 1 - 2 covering about 1/4 of the bushings circumference.

My question here

is there a top or bottom (and thereby installed incorrectly)?

is this left mount deffective ( indentation are not supposed to be there)?

could somebody check there car to verify this?

BTW, Damn I am sick of this also!!

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