Ls Vibration Problem

[JimsGX]

Hi,

I bought a 91 LS400 a couple of weeks ago with 76,300 miles on it. It's a one owner vehicle and I know the previous owner. She is 76 years old and only drove it on the weekends. Every service was performed by the local Lexus Dealer (I have a copy of every single service record) and its had all the standard major service performed including the timing belt, water pump, steering rack, PS pump, all new brakes and rotors just 2k miles ago and only 3k miles on the tires. I've put about 500 miles on it over the last couple weeks and started to notice a vibration about 100 miles ago. I've searched and read all the threads on this subject but haven't really found a condition just like the one I'm experiencing. The car has a vibration only when decelerating at 29 down to 25mph. Then it has it again when cruising at 47 to 56mph and decelerating at the same speed. When accelerating, either the drivetrain is masking the vibration or it doesn't exist. Also, under any of these conditions, I can put my hand on the shifter, and there's absolutely no transfer of the vibration coming through the shifter. At either of these speeds, if I put the vehicle in neutral, the vibration is exactly the same. Once I coast down out of those speed ranges, the vibration goes away. I had the tires rebalanced this past weekend and it made no difference at all in the vibration. I can put the vehicle in park and rev it up to 4000rpm and its smooth as silk with no vibration at all. Also, under the conditions above when its vibrating, there's no vibration being transferred through the steering wheel. I can cruise at 75mph with just one finger on the wheel. It drives straight and true...

Any idea's? I know one of the more common recommendations is to replace the motor and transmission mounts but in this case I don't know if that would do any good...

Thanks,

Jim

[landar]

Jim,

First off, congrats on such a rare find. Sounds like you made a wise purchase.

Since you mention that the vibration is on decel, it makes me question the wheel bearings.

The reason I say this is because I had a Subaru long ago that did something similar...it would be

noisy upon decel and nothing when accelerating. When you accel or decel, you shift(slightly) the load

point on the bearings and get different responses.

That said, I am simply shooting in the dark. More often than not, it is a bad tire though it appears fine.

You will have to do your own due diligence to determine if there is any merit. As I like to say, do your own do-do

If the wheel bearings have never been touched and the cost is not too high, it may just be good preventative maintenance anyway.

Go on, the old girl deserves it! ...and so does the car :whistles:

[JimsGX]

Jim,

First off, congrats on such a rare find. Sounds like you made a wise purchase.

Since you mention that the vibration is on decel, it makes me question the wheel bearings.

The reason I say this is because I had a Subaru long ago that did something similar...it would be

noisy upon decel and nothing when accelerating. When you accel or decel, you shift(slightly) the load

point on the bearings and get different responses.

That said, I am simply shooting in the dark. More often than not, it is a bad tire though it appears fine.

You will have to do your own due diligence to determine if there is any merit. As I like to say, do your own do-do

If the wheel bearings have never been touched and the cost is not too high, it may just be good preventative maintenance anyway.

Go on, the old girl deserves it! ...and so does the car :whistles:

HaHa! Thanks... I'm taking it to a mechanic this weekend to get it up on a lift and check it out. Might very well be a wheel bearing. I took off each wheel this evening, replaced each with my spare, then did a test drive after each swap. The vibration was still consistently there after each swap so I think I've definitley ruled out the tires and rims. Hopefully a visual of the driveline and a suspension check will reveal something this weekend.

For 20 years or more now, my wife and I have been fortunate enough to always have new cars under warranty, so I haven't had to worry about finding a good (and honest) mechanic since most repairs have been minimal and through the dealers. Finding a good mechanic for the old Lexus might be my biggest challenge at the moment. I don't plan on paying through the nose for repairs on a 91 LS at the dealer. Some of the invoices I have for the repairs done by the previous owner were rediculously high. They were even hitting her up for a periodic engine steam clean.

When you had the wheel bearing problem on the Subaru, were you getting any kind of howling noise and/or was the vibration worse when cornering?

Thanks,

Jim

[SRK]

It's not a wheel bearing.

However it could be driveshaft alignment or a trans or engine mount.

[landar]

Jim,

Yes, on the Subaru, the wheel bearing in the front would make a grinding/howling sound only when decelerating. I really

dont recall exactly what it did on cornering, though I believe it aggrevated it in one direction and not in the other.

That might be something to try if you could be taking a slight corner while decelling at your 25 mph. Try right and left noting

any difference.

I think you are wise taking it to a mechanic. Even though I am a DIY'er, I occasionally take my cars to a specialist

for an opinion as to what might be wrong and I pay them for their time (sometimes its free). I then take it home and do the work myself.

Now, the best mechanic for your car can be found by looking into any mirror in your house (make sure your wife is not

standing next to you!). The good thing about your situation is that this is not "life-threatening". You can take your time(and save money)

by carefully studying and deducing/determining the problem. BTW, mechanics can be fooled so if you have doubts about the diagnosis,

try a second opinion. I even do this with doctors and its amazing the differences I sometimes get. One will be 'experimenting' (practicing

medicine actually ) and the other will have seen it before and know exactly whats wrong.

You didnt really mention any sounds in the orginal post. Are there any associated sounds with the vibration? And if so,

can you describe?

[JimsGX]

Jim,

Yes, on the Subaru, the wheel bearing in the front would make a grinding/howling sound only when decelerating. I really

dont recall exactly what it did on cornering, though I believe it aggrevated it in one direction and not in the other.

That might be something to try if you could be taking a slight corner while decelling at your 25 mph. Try right and left noting

any difference.

I think you are wise taking it to a mechanic. Even though I am a DIY'er, I occasionally take my cars to a specialist

for an opinion as to what might be wrong and I pay them for their time (sometimes its free). I then take it home and do the work myself.

Now, the best mechanic for your car can be found by looking into any mirror in your house (make sure your wife is not

standing next to you!). The good thing about your situation is that this is not "life-threatening". You can take your time(and save money)

by carefully studying and deducing/determining the problem. BTW, mechanics can be fooled so if you have doubts about the diagnosis,

try a second opinion. I even do this with doctors and its amazing the differences I sometimes get. One will be 'experimenting' (practicing

medicine actually ) and the other will have seen it before and know exactly whats wrong.

You didnt really mention any sounds in the orginal post. Are there any associated sounds with the vibration? And if so,

can you describe?

Hi Again,

I'm not hearing any noises coming from the wheels when going straight or turning. I tend to agree with SRK's comment above that it is drive line related. I'll post when I find out what the root cause is (hopefully).

Thanks!

Jim

[carlhpretired]

It's not a wheel bearing.

However it could be driveshaft alignment or a trans or engine mount.

Engine and/or transmission mounts are a good possibility. I have a 1990 LS 400 (246K miles) and

had a similar problem - new engine mounts fixed it.

Test: With the engine idling and transmission in PARK, depress accelerator slowly and increase engine

RPM to 2300 or so. If you notice a shuddering that increases and decreases as you move through the

600 to 2300 RPM range, it's an absolute indication that your engine mounts need to be replaced.

[teamer]

Jim,

I have the same problem you have and for me it was the tires.

The tires, although you re-balanced them, maybe improperly worn - meaning you may have a slight alignment problem. If this is the case, you could not detect it with the naked eye just by looking at the tires. It might be slightly off than ideal and this could cause vibration problems at certain speeds (due to harmonic vibrations).

I know you might not have spare tires available, but, as a test, I would replace all 4 wheels temporarily and drive it and see if there's a difference. This could save you the costly expense of replacing motor mounts, transmission mounts, driveline axles, etc. only to find out that it was just the tires...

If you happen to know of another friend with an LS400 year 90-92, and he/she would allow you to swap tires, then this might be a cost effective test to troubleshoot.

It would be a shame if spent money on parts that did not need to be replaced.

Just my 2 cents... Hope you can find out the root of the problem...Good luck....

Teamer

[Jerry Bransford]

I agree on having the tires checked first. Many speed sensitive vibrations are tire related so I'd have them carefully checked and perfectly balanced. Only after doing that and it not fixing it would I look into the other possible sources. Always look at the easy causes first, THEN look at the more involved/expensive possible causes. :)

[JimsGX]

Jim,

I have the same problem you have and for me it was the tires.

The tires, although you re-balanced them, maybe improperly worn - meaning you may have a slight alignment problem. If this is the case, you could not detect it with the naked eye just by looking at the tires. It might be slightly off than ideal and this could cause vibration problems at certain speeds (due to harmonic vibrations).

I know you might not have spare tires available, but, as a test, I would replace all 4 wheels temporarily and drive it and see if there's a difference. This could save you the costly expense of replacing motor mounts, transmission mounts, driveline axles, etc. only to find out that it was just the tires...

If you happen to know of another friend with an LS400 year 90-92, and he/she would allow you to swap tires, then this might be a cost effective test to troubleshoot.

It would be a shame if spent money on parts that did not need to be replaced.

Just my 2 cents... Hope you can find out the root of the problem...Good luck....

Teamer

Thanks... Well, Since your in Texas and I'm in Massachusetts, why don't we meet in Kentucky and swap tires & rims! I'll bring the beer!

Thanks for the info... I'm having the transmission mount and steering damper replaced tomorrow... They're telling me the steering damper is junk (leaking)... I figured I'd go as far as the tranny mount because its not a very big expense. From there, I'm going back to the tires. I had all four balanced on a hunter machine and it didn't make any difference. They're Sumitomo tires (they make the Dunlop brand for the Asian market). They only have a few thousand miles on them...

What brand of tires and how many miles were on them when you had the problem?

Thanks,

Jim

[1990LS400]

Odd vibrations at different speeds can also be caused by worn front suspension bushings. Some of the front suspension bushings on the early LS400 was known for premature failure. Some the original front suspension bushings on the 90 LS I bought in 1990 were replaced at no cost before the basic warranty expired simply because of the noise they were making.

[teamer]

Jim,

I used to live in Massachusetts - Newton/Boston - too bad, we could've swapped had I been there!

The brand I have are Yokohamas, but, again, it doesn't matter what brand of tire - it was the alignment that caused the problem. If your car is not properly aligned, your tires (no matter how great they are) will wear un-evenly and eventually will give you that vibration at certain speeds. So even if your tires are re-balanced perfectly, if they are already worn un-evenly it won't change anything.

Hope you find the cause of the problem soon - I know how annoying it is to hear that noise when driving-especially in a car that was designed to be quiet.

Cheers!

Teamer

[JimsGX]

For a second time last night I took each tire off, replaced it with the spare and test drove it. Each time it didn't make any difference. The tires have around 3k miles on them. I had them rebalanced on a Hunter machine a week and a half ago. This past weekend, I had a four wheel alignment done on a Hunter alignment machine. The left front was only slightly out of spec and all others were within spec. They gave me a color print out that showed the before and after results. Again, it didn't change anything.

Tonight the Steering Damper and Transmission mount are being replaced. The steering damper is leaking fluid. I'm doing the tranny mount while its in the shop, only because its an inexpensive replacement that so many on this site have either had a problem with or seen an improvement from after installing. If these don't fix it (which I'm pretty sure they won't) I may take a break from trying to troubleshoot it and wait until it gets worse / more easily identifiable... I did see a TSB somewhere that spoke about changing the stabilizer bushings on the earlier Lexus LS's... I believe it replaced them with teflon coated ones in order to stop squeaking.

Does anyone care to guess what the average life span of the struts / shocks are on the older LS's (91)? For all of these parts, I think age and drying out of the rubber components are as much a contributing factor to their failure as is mileage. My 91 only has 77k miles on it.

Thanks...

[kmpdd]

Odd vibrations at different speeds can also be caused by worn front suspension bushings. Some of the front suspension bushings on the early LS400 was known for premature failure. Some the original front suspension bushings on the 90 LS I bought in 1990 were replaced at no cost before the basic warranty expired simply because of the noise they were making.

[kmpdd]

Odd vibrations at different speeds can also be caused by worn front suspension bushings. Some of the front suspension bushings on the early LS400 was known for premature failure. Some the original front suspension bushings on the 90 LS I bought in 1990 were replaced at no cost before the basic warranty expired simply because of the noise they were making.

[kmpdd]

Odd vibrations at different speeds can also be caused by worn front suspension bushings. Some of the front suspension bushings on the early LS400 was known for premature failure. Some the original front suspension bushings on the 90 LS I bought in 1990 were replaced at no cost before the basic warranty expired simply because of the noise they were making.

That's interesting. What bushings would those be? thanks

[pishta]

Odd vibrations at different speeds can also be caused by worn front suspension bushings. Some of the front suspension bushings on the early LS400 was known for premature failure. Some the original front suspension bushings on the 90 LS I bought in 1990 were replaced at no cost before the basic warranty expired simply because of the noise they were making.

That's interesting. What bushings would those be? thanks

any update on the trans mount having any impact, how about the steering damper? there are a couple of us that are in the same boat in the vibration department. Mine must have been the little old man story, '92 with 93k on it, Old doctors that was retired and drove it to the golf course every weekend, since deceased so I hope the stereo doesnt have a security code on it! All records back to the original receipt, $52,760 out the door!!! It also has receipts for 3 different tire changes and the ones Im riding on now, that is 4 sets before 100k! Too bad he could pony up for the fender ding before he sold it to me....

[zenmaster52]

I have a 1990 LS 400 with 82000 miles. It veers to the right and I feel the vibration in steering wheel at speeds above 65 mph. I had the alignment done and the tires checked but the problem remains. My mechanic says that the front wheel bearing assembly and lower ball joints need to be replaced. Any suggestion?

[JimsGX]

Odd vibrations at different speeds can also be caused by worn front suspension bushings. Some of the front suspension bushings on the early LS400 was known for premature failure. Some the original front suspension bushings on the 90 LS I bought in 1990 were replaced at no cost before the basic warranty expired simply because of the noise they were making.

That's interesting. What bushings would those be? thanks

any update on the trans mount having any impact, how about the steering damper? there are a couple of us that are in the same boat in the vibration department. Mine must have been the little old man story, '92 with 93k on it, Old doctors that was retired and drove it to the golf course every weekend, since deceased so I hope the stereo doesnt have a security code on it! All records back to the original receipt, $52,760 out the door!!! It also has receipts for 3 different tire changes and the ones Im riding on now, that is 4 sets before 100k! Too bad he could pony up for the fender ding before he sold it to me....

Hi,

The Transmission Mount and Damper replacement didn't fix the problem. I think the damper helped but it was unrelated to the primary vibration issue which hasn't changed. The car is going into the local Lexus dealer this Wednesday for a diagnostic. Hopefully they can isolate it. If / when they figure it out, I'll post the fix.

Thanks

Jim

[JimsGX]

Hi,

Here’s My Vibration Update…

I took my 1991 LS to the dealer today to have them diagnose a driveline vibration problem. The car only has 78,000 miles on it. The mechanic that worked on the vehicle has been with the same Lexus dealership since 1992 and seemed very knowledgeable. He knows the old LS’s in’s and out’s. He came back with the following recommendations:

1.) The propeller shaft spline and carrier bearing have some play in them but really aren’t all that bad.

2.) The exhaust Y pipe that connects to the two catalytic converters and leads back to the mufflers is an aftermarket pipe that doesn’t fit as well as the OEM pipe. The aftermarket Y pipe doesn’t have the proper bends in it, and is forcing the two mufflers up closer to the underside of the floorboards and propeller shaft than they should be. This in turn is putting down pressure on the two catalytic converters, which is also having the effect of ever so slightly changing the attitude of the engine on its mounts, which is then causing the driveline alignment problem.

3.) They checked out all steering and suspension parts and found things that were of little consequence that they wouldn’t even recommend I do anything about at this point. The upper control arms have a little play but are okay, they aren’t making any clunking noises. The sway bar bushings have cracks in them but don’t squeak. The power steering solenoid has a very slight leak (the whole rack and pump were replaced about 8k miles ago by Lexus so what’s up with this?). The power assist doesn’t kick out at high speed, so the steering is always super easy. A bit too easy at highway speeds. This is either being caused by a defective solenoid or defective ECU. He said if it’s the ECU, it’s a $500 fix.

So, I think the vibration problem is being caused by the Y pipe. I had it installed six weeks or so ago. I’ve only owned the vehicle for seven weeks or so. The day after the Y pipe was installed is when I noticed the vibration. I had brought it back to the muffler shop two days later to have them recheck their work when the vibration started, but they said everything was fine. I figured the two were pure coincidence, but now I’m thinking otherwise. I may have a fight on my hands to get them to take back the aftermarket pipe unless their supplier is willing to eat it. I had it installed for $884… The OEM pipe is very expensive. I think dealer list is around $1300+-…

For those of you with the vibration problem, how many have after market Y pipes or other exhaust components on their vehicles? I’d bet a good percentage of us do because of the costs associated with keeping it OEM…

As many of us know first hand, and the mechanic repeated to me today, the early Lexus vehicles, and even many of the newer ones, tend to have a lot of vibration issues and are very sensitive to alignment and wheel balancing issues. He’s learned over the years to fine tune the alignment specs on certain vehicles even further within the recommended Lexus spec’s in order to get rid of some vibrations.

Does anyone know of a good online source ($$) for purchasing the OEM Y pipe?

As far as the power steering problem, is this the same ECU that controls the engine? If it is, would disconnecting the battery possibly reset the ECU and fix my steering assist problem if it is the ECU? If I try this, is there a reset procedure for the windows and sunroof on the early LS’s like my new RX/GX vehicles? I looked through the owner’s manual briefly this evening but didn’t find a reset procedure.

Thanks,

Jim

[Canopy]

Hi,

Here’s My Vibration Update…

I took my 1991 LS to the dealer today to have them diagnose a driveline vibration problem. The car only has 78,000 miles on it. The mechanic that worked on the vehicle has been with the same Lexus dealership since 1992 and seemed very knowledgeable. He knows the old LS’s in’s and out’s. He came back with the following recommendations:

1.) The propeller shaft spline and carrier bearing have some play in them but really aren’t all that bad.

2.) The exhaust Y pipe that connects to the two catalytic converters and leads back to the mufflers is an aftermarket pipe that doesn’t fit as well as the OEM pipe. The aftermarket Y pipe doesn’t have the proper bends in it, and is forcing the two mufflers up closer to the underside of the floorboards and propeller shaft than they should be. This in turn is putting down pressure on the two catalytic converters, which is also having the effect of ever so slightly changing the attitude of the engine on its mounts, which is then causing the driveline alignment problem.

3.) They checked out all steering and suspension parts and found things that were of little consequence that they wouldn’t even recommend I do anything about at this point. The upper control arms have a little play but are okay, they aren’t making any clunking noises. The sway bar bushings have cracks in them but don’t squeak. The power steering solenoid has a very slight leak (the whole rack and pump were replaced about 8k miles ago by Lexus so what’s up with this?). The power assist doesn’t kick out at high speed, so the steering is always super easy. A bit too easy at highway speeds. This is either being caused by a defective solenoid or defective ECU. He said if it’s the ECU, it’s a $500 fix.

So, I think the vibration problem is being caused by the Y pipe. I had it installed six weeks or so ago. I’ve only owned the vehicle for seven weeks or so. The day after the Y pipe was installed is when I noticed the vibration. I had brought it back to the muffler shop two days later to have them recheck their work when the vibration started, but they said everything was fine. I figured the two were pure coincidence, but now I’m thinking otherwise. I may have a fight on my hands to get them to take back the aftermarket pipe unless their supplier is willing to eat it. I had it installed for $884… The OEM pipe is very expensive. I think dealer list is around $1300+-…

For those of you with the vibration problem, how many have after market Y pipes or other exhaust components on their vehicles? I’d bet a good percentage of us do because of the costs associated with keeping it OEM…

As many of us know first hand, and the mechanic repeated to me today, the early Lexus vehicles, and even many of the newer ones, tend to have a lot of vibration issues and are very sensitive to alignment and wheel balancing issues. He’s learned over the years to fine tune the alignment specs on certain vehicles even further within the recommended Lexus spec’s in order to get rid of some vibrations.

Does anyone know of a good online source ($$) for purchasing the OEM Y pipe?

As far as the power steering problem, is this the same ECU that controls the engine? If it is, would disconnecting the battery possibly reset the ECU and fix my steering assist problem if it is the ECU? If I try this, is there a reset procedure for the windows and sunroof on the early LS’s like my new RX/GX vehicles? I looked through the owner’s manual briefly this evening but didn’t find a reset procedure.

Thanks,

Jim

I have purchased several parts at Irontoad.com and have found them to be very reasonable in price with excellent service. I normally receive the parts within 2-3 days. If it were me, I'd try them first. Good luck. Thanks for all of the details on your problem; it makes it an interesting (to us) puzzle.

[swordfish]

i tire of telling the tale, but it is true, the Lexus LS 400 is a unique vehicle- the fact it is one of the quietest and smoothest cars ever made is due to the extensive and unbelievable lengths those 1400 Japanese engineers went to over the 8 or something years they developed the car. It is so smooth and quiet because the sound and vibration isolation techniques used were very sophistocated and cutting edge. Fact: vibration at 110kph = 70 mph on highway, in seats and body, not in steering, balance rear wheels to fix. note: balance very accurately- have been to experts at Goodyear shop and they say, " buddy the balance isnt out enough to cause a vibration, you must have another problem, bent rim or something" and i say, "thats ok, just go ahead and do the balance as accurate as you can" they say "ok but it wont do any good" Go onto highway, guess what ?? problem fixed.

Reason: LS 400 is so smooth and quiet because suspension bushes and rubbers are very soft and complient to absorb all those running vibrations, a small out of balance wheel, tyre or tailshaft bearing and it blows the whole game. And as we see above, a exhaust Y pipe putting pressure on rear mount also causing a vibration drama. I have also had a rear trans mount collapse and that caused horrible ammounts of different vibrations and even if you revved engine in neutral the car would suddenly accelerate, because the clutch plates in the auto were vibrated into gear momentarily.

All the moving masses: engine,transmission, suspension etc, they are like a finely pitched tuning fork, one touch at the wrong place and you cause a vibration trauma. everything must be in harmony.

The point here is you cant diagnose these problems by saying " i had a subaru once and it did so and so" this car is unique and experiences with other makes do not necessarily count for much.