92 Ls400 Vibration At 70-80 Mph

[WeSki]

I have 174K on my 92 LS400 and for a year I have had a noticeable amount of vibration at speeds of 70 to 80 MPH with the vibration at its greatest at 75 MPH. The vibration only occurs at the mentioned speed, not in park at any RPM, and not at lower around town speeds. The vibration seems to come up from the floor and you feel it in your seat and then all over at 75MPH.

I have recently bought new tires (Michelin Energy MXV4Plus XSE) and had the rotors turned and the vibration remained the same. I had the car test driven and inspected be a shop that specializes in Lexus and Toyota. The struts and strut mounts are original yet in good condition. The tranny mount is in great shape appearing to be new; I have owned the car for 5 years so the previous owner my have replaced it. The motor mounts are showing their age but intact. The lower ball joints have some play. By what I have read and in talking to the mechanic the opinion is that the vibration we are experiencing is not one that would be caused by the lower ball joints.

One thing I have not read much about in this forum is vibration related to the drive line and or carrier bearing. Shifting between reverse, neutral, and drive is very quite and smooth. I have had a similar vibration on a domestic truck and replacing the carrier bearing did the trick..

Please share your ideas and opinions.

[UCF3]

Sounds like a wheel vibration. Have you tried to have you wheels re-balanced?

[WeSki]

Sounds like a wheel vibration. Have you tried to have you wheels re-balanced?

Help me out; when you say wheels re-balanced are you talking about checking the balance of the wheel only (no tire mounted) or are you talking about a standard tire balance? I had the tires balanced and rotated 3 weeks ago and there was no excessive amount or large balancing weight used on any wheel. This balancing did not help reduce the vibration.

[chrisnisbet]

I have a '95 LS400 with much the same problem. At certain speeds, a virbration comes up through the car and can even produce a droning kind of noise. We finally tracked it down to the driveshaft. Replacing the couplings at each end of the driveshaft made no difference. In the end, we replaced the driveshaft itself (with a second hand one as the price of a new one was horrendous (NZ$5K)). The problem hasn't _completely_ gone away. I still get a bit of vibration at about 70kph, but nothing like what I had before. All other speeds are pretty good now. We considered balancing the original, but the balancing people said that my driveshaft had too much play in the splines that connect the front and rear portions together. I just put up with the little bit of vibration that is left.

Apparently, it is also quite important to get the alignment of the driveshaft correct when installing it.

personally, it seems like a bit of a design issue to me. The idea of a mounting point in the middle of the driveshaft connecting it to the car seems like a likely spot for any slight out of balance condition in the driveshaft to be transferred to the car

[WeSki]

I took the car to the shop, had the mechanic test drive the car and look it over on the hoist. He allowed me under the car and we looked at a number of things.

The Transmission mount is in great shape in fact it looks new. The mechanic put a lift under the trany and lifted it up and down slightly to check the movement of the mount, looked great. The engine mounts are looking tired yet in tacked.

The lower ball joints have some play and should be replaced soon however, based on the test drive the mechanic did not feel that this was the source of the vibration.

We could not get a good look at the drive line as it is behind the exhaust and heat shield.

I think my next DIY will be to pull the drive line and have it checked out. If there are any tips or suggestions out there on how to do this job please share it with me. Also while I’m at it I think I’ll replace the lower ball joints.

[chrisnisbet]

I'd be interested to hear how it turns out. Is your vibration accompanied by a kind of low frequency droning noise? With my car, the actual vibration isn't too noticeable any more, but I still notice the funny droning kind of noise. The noise is a little bit similar to what you can get if one of the windows is left open while driving along.

[eerrrrr]

have u checked ur brake rotors. if they r kinda warped, u will have slight vibration also. or they might need a resurface job.

[nc211]

Ahhh. now this is my kind of stuff, as I suffered dearly with vibrations in the early years.

Chris, that droning noise you're hearing can be greatly reduced with the replacement of the two rear differential mounts. If you look at the differential from the rear of the car, on the top portion of the differential along the crossmember, you'll see two medium sized donut hole mounts. The driver's side will crack, and cause vibration and droning noises. You'll have to get an indi shop to get them out, as they're pressed in there pretty tightly. You have to actually lower the differential to get them pressed out, and they come out towards the front of the car, not the rear. Not too expensive. I think they're like $40 each, and there are only two of them. Makes a difference!

Warped rotors on a toyota for some reason will really transmit vibration throughout the car. My 4Runner has warped rotors, and need to be turned. I know they're warped, as the truck pulsates when coming to a stop, but it also shimmies a bit under normal driving conditions, especially in the rears.

[nc211]

I have 174K on my 92 LS400 and for a year I have had a noticeable amount of vibration at speeds of 70 to 80 MPH with the vibration at its greatest at 75 MPH. The vibration only occurs at the mentioned speed, not in park at any RPM, and not at lower around town speeds. The vibration seems to come up from the floor and you feel it in your seat and then all over at 75MPH.

I have recently bought new tires (Michelin Energy MXV4Plus XSE) and had the rotors turned and the vibration remained the same. I had the car test driven and inspected be a shop that specializes in Lexus and Toyota. The struts and strut mounts are original yet in good condition. The tranny mount is in great shape appearing to be new; I have owned the car for 5 years so the previous owner my have replaced it. The motor mounts are showing their age but intact. The lower ball joints have some play. By what I have read and in talking to the mechanic the opinion is that the vibration we are experiencing is not one that would be caused by the lower ball joints.

One thing I have not read much about in this forum is vibration related to the drive line and or carrier bearing. Shifting between reverse, neutral, and drive is very quite and smooth. I have had a similar vibration on a domestic truck and replacing the carrier bearing did the trick..

Please share your ideas and opinions.

Have you checked the tranny mount recently? Cheap and easy diy fix.

[UCF3]

Sounds like a wheel vibration. Have you tried to have you wheels re-balanced?

Help me out; when you say wheels re-balanced are you talking about checking the balance of the wheel only (no tire mounted) or are you talking about a standard tire balance? I had the tires balanced and rotated 3 weeks ago and there was no excessive amount or large balancing weight used on any wheel. This balancing did not help reduce the vibration.

I apologize for not checking the forum. Re-balancing means just like it sounds, take your brand new wheels and tires and have them put new weights on.

there maybe more too it than what I was thinking it would be. Did you or the mechanic check the bearings, and have you isolated the side of the vibration? Also, check the tires themselves just in case the tire-belts on one of them is going bad-yes it happens to new ones as well( you could use the spare to isolate one wheel at a time). Are you seeing any lights like the Trac lights or ABS flashing.

Also, if you have more information on when you're experiencing the problem other than at high speeds that would also be helpful--road conditions, when you noticed it for the first time etc

Vibrations are based on contact with the road. it has to lie with the items that are making contact with the surface. Wheels and tires would be guess without looking.

[chrisnisbet]

NC211, it's interesting that you should mention those diff mounts. It's a bit of a long story, but it wasn't until I had them replaced (I'm not 100% sure they're the ones you are talking about, but there are a total of 4 diff mounts from what I was told, and I had them all replaced) that I first noticed the vibration. Before then, my car rolled along as smooth as silk. I went to get a warrant of fitness one day, and the mechanic (independant) noticed that two of the mounts were cracked. Didn't cost me much at all because I have a warranty that covers most of those things. Anyway, got the car back and noticed this vibration/noise. Quite minor, and thought it might be a wheel balance issue. Got them balanced, and the tire guy told me that the two rear tyres were out of round, and could be causing the vibration. Anyway, because I don't drive the car much, I just put up with it. After some time though, the vibration suddenly got _really_ bad. Couldn't travel more than 60kph. Took the car back, and they found that they hadn't installed one of the driveshaft couplings correctly. They replaced the front and rear driveshaft couplings because one was destroyed (due to error during diff job). Fixed that up, and I was back to where I was before. Finally got my two rear tyres replaced, and vibration didn't change at all. Vibration got a bit worse, and I thought I'd nag the service people about it. Went to get driveshaft balanced, but balancers said that there was too much play in splines to do a decent job. Got a different driveshaft, and vibration is better, but not completely gone. I've had a gutsful of it now and just put up with what is left. I'm left with the feeling that it is pretty easy for something to be slightly off in the drivetrain, resulting in a vibration/drone noticeable in the cabin.

[nc211]

NC211, it's interesting that you should mention those diff mounts. It's a bit of a long story, but it wasn't until I had them replaced (I'm not 100% sure they're the ones you are talking about, but there are a total of 4 diff mounts from what I was told, and I had them all replaced) that I first noticed the vibration. Before then, my car rolled along as smooth as silk. I went to get a warrant of fitness one day, and the mechanic (independant) noticed that two of the mounts were cracked. Didn't cost me much at all because I have a warranty that covers most of those things. Anyway, got the car back and noticed this vibration/noise. Quite minor, and thought it might be a wheel balance issue. Got them balanced, and the tire guy told me that the two rear tyres were out of round, and could be causing the vibration. Anyway, because I don't drive the car much, I just put up with it. After some time though, the vibration suddenly got _really_ bad. Couldn't travel more than 60kph. Took the car back, and they found that they hadn't installed one of the driveshaft couplings correctly. They replaced the front and rear driveshaft couplings because one was destroyed (due to error during diff job). Fixed that up, and I was back to where I was before. Finally got my two rear tyres replaced, and vibration didn't change at all. Vibration got a bit worse, and I thought I'd nag the service people about it. Went to get driveshaft balanced, but balancers said that there was too much play in splines to do a decent job. Got a different driveshaft, and vibration is better, but not completely gone. I've had a gutsful of it now and just put up with what is left. I'm left with the feeling that it is pretty easy for something to be slightly off in the drivetrain, resulting in a vibration/drone noticeable in the cabin.

4 of them? Interesting... I only have two, and an attachment bolt on the passenger side. That attachment bolt bracket has a rubber bushing on it as well, that insulates the differential from the frame. One thing that could of happened when they did the other bushings is that they over or under tighetend that bolt, which could cause the differential to line up just a slight bit out of sync. It needs to be pretty dead-on straight. And, or, that rubber ring could be worn out that sits between the bolt housing and the car....

[chrisnisbet]

I must admit, I didn't bother to take too close a look under the car myself. I was only going by what the mechanics told me. Next time I take the car in for a service, I'll mention what you've said about those mounts though. I might take a peek to see if I can see the mounts they/you are talking about.

[nc211]

http://us.lexusownersclub.com/forums/index...ntial&st=15

http://us.lexusownersclub.com/forums/index...erential+mounts

Chris, there are a couple of attachments and a photo of the mounts in the two threads above. I pretty sure our differentials are mounted the same way...

[chrisnisbet]

Hi

I guess they were talking about the two rear mounts which attach to the crossmember, and the two 'mount stoppers' which go at the front of the diff ether side of the drifeshaft coupling.

[SKperformance]

Sounds like they replaced the bushings and screwed up getting the drive shaft and diff back into proper alignment . By having it off center it caused a vibration and caused the ends to wear which is why it cannot be rebalanced.

[chrisnisbet]

I suspect you are right SK. The problem doesn't seem too bad now with the new (second hand) shaft. Mostly, I'm the only person than can actually notice it now. The guys at the shop can't really tell what I'm going on about. I'm reluctant to give them a hard time about it because they have tried pretty hard to resolve this for me (at their expense).

All told, we've replaced the diff mounts, the driveshaft couplings, and replaced the old sloppy shaft with a second hand one. It would have been nice to get a new shaft as well, but the cost was about NZ$5K, and I would have had to stump up a lot of the cash for that (my warranty doesn't stretch that far).

I just remember the way it used to roll along so smootly, and wish it was like that again. I guess we could have a go at balancing the second shaft.

[JimsGX]

Ahhh. now this is my kind of stuff, as I suffered dearly with vibrations in the early years.

Chris, that droning noise you're hearing can be greatly reduced with the replacement of the two rear differential mounts. If you look at the differential from the rear of the car, on the top portion of the differential along the crossmember, you'll see two medium sized donut hole mounts. The driver's side will crack, and cause vibration and droning noises. You'll have to get an indi shop to get them out, as they're pressed in there pretty tightly. You have to actually lower the differential to get them pressed out, and they come out towards the front of the car, not the rear. Not too expensive. I think they're like $40 each, and there are only two of them. Makes a difference!

I'm experiencing the exact same droning noise that Chris is on my 1991 LS400 with 77k miles on it. I've had the suspension checked and they can't find any parts that are worn, I had the tires rebalanced, a four wheel alignment, replaced the transmission mount today as well as the steering damper. The vibration is still there. The sound described, like having the back window down and hearing that wap wap sound that resonates in your ears is exactly how I explained it to the mechanic. It sounds / feels like its coming more from the center or rear of the car. I'm usually pretty good at pin pointing the location of these types of things but this one has been elusive. Mine is most obvious at 25 to 29mph, then again at around 50mph. It isn't as bad when accelerating, more when going at an even speed or when decelerating... Also, most of the time when the car has been sitting overnight, it takes anywhere from 3 to 10 miles of driving before it starts acting up again. Almost as if a bushing is starting to work itself / warm up and become more flexible and then the vibration shows up... Can you tell me if these conditions are similar to what you experienced nc211, and what you were noticing before, and to a lesser extent now Chris?

Thanks,

Jim

[chrisnisbet]

Yep, exactly. That business of being a bit worse/different first thing in the morning matches what I experience as well. From what I have read on this forum, and from my own experiences, it strikes me that it doesn't take much of a misalignment in the drivetrain alignment (diff/tranny mounts etc.) before this vibration rears its ugly head. Another thing I found was that with each new attempt at trying to resolve the problem, the vibration would occur at slightly different speeds. (I had the driveshaft dropped out a few times, and the diff mounts checked.) One of the hardest things to do I've found is convincing people that the vibration even exists. Odd, because it's plainly obvious to me.

[JimsGX]

Thanks Chris,

I think my problem is the same as yours. My differential only has one side bracket on it. On the passenger side. I plan to get under the car this weekend and check everything out close up. If I decide to repair it, which I think I'll have to because its driving me nuts, I'll do the three differential mounts, maybe a new bracket, and the shaft center bearing while its all apart... I haven't seen anthing in searching in the message threads about center shaft bearing failure. I only have 77k miles (124k kilometers) on the vehicle so hopefully I won't have a shaft spline problem.

When the mechanic test drove the vehicle with me, he couldn't feel (or hear) the vibration. It was so obvious to me, I think each of us thought the other was nuts. I joked with him and asked him if he had the shakes from drinking too much the night before. He admitted to downing a few.

Do you know if the center bearing needs to be greased periodically or is it a sealed unit? I've seen some generic references to lubricating the bearing but in looking through the LS400 repair manual on alldata, I haven't seen any specific info for the LS.

Thanks

Jim

[chrisnisbet]

Nope, no idea if any of these bits and pieces need greasing. I saw the cracks in the diff mounts, and they need a fairly close inspection to spot. I guess one day I'll get around to seeing if I can get this sorted.

[WeSki]

No noise that I can tell at this point.

[WeSki]

I took the car to the shop, had the mechanic test drive the car and look it over on the hoist. He allowed me under the car and we looked at a number of things.

The Transmission mount is in great shape in fact it looks new. The mechanic put a lift under the trany and lifted it up and down slightly to check the movement of the mount, looked great. The engine mounts are looking tired yet in tacked.

[lht]

Check you front calibers may be one of them got stuck. I bet ya 100%

lht

I have 174K on my 92 LS400 and for a year I have had a noticeable amount of vibration at speeds of 70 to 80 MPH with the vibration at its greatest at 75 MPH. The vibration only occurs at the mentioned speed, not in park at any RPM, and not at lower around town speeds. The vibration seems to come up from the floor and you feel it in your seat and then all over at 75MPH.

I have recently bought new tires (Michelin Energy MXV4Plus XSE) and had the rotors turned and the vibration remained the same. I had the car test driven and inspected be a shop that specializes in Lexus and Toyota. The struts and strut mounts are original yet in good condition. The tranny mount is in great shape appearing to be new; I have owned the car for 5 years so the previous owner my have replaced it. The motor mounts are showing their age but intact. The lower ball joints have some play. By what I have read and in talking to the mechanic the opinion is that the vibration we are experiencing is not one that would be caused by the lower ball joints.

One thing I have not read much about in this forum is vibration related to the drive line and or carrier bearing. Shifting between reverse, neutral, and drive is very quite and smooth. I have had a similar vibration on a domestic truck and replacing the carrier bearing did the trick..

Please share your ideas and opinions.

[JimsGX]

Here are some pictures of my differential mounts... The two rear mounts and the mount on the bracket. The right side mount doesn't look too bad but the left side mount has a totally different appearance. I think the bracket mount is looking pretty shabby too. This is a 1991...

The pictures are pretty hi res, close to 2mb each. You'll need Acrobat v7 or later to open.

Any opinions on the condition of these?

Thanks

LS400_Diff_Mount___Left.pdf

LS400_Diff_Mount___Right.pdf

LS400_Diff_Mount_Bracket.pdf