Driveline Vibration Between 35-40mph

[Sweet95LS400]

I noticed this when I bought the car, but it has gotten a little worse. There is a vibration when accelerating between 35-40MPH. I have tried to replace the basics but nothing has changed it, I replaced the transmission mount, differential fluid, transmission fluid and brakes. No change. It is most apparent when there are 4 people in the car and you accelerate up a hill. Or if you drive more aggressively. All the shifts are smooth and it only does it at that speed range. I am stumped on this one. I mentioned it to my Lexus dealer and they said they didnt feel anything. So I guess I am on my own on this one.

Any ideas?

[Leadfoot]

I mentioned it to my Lexus dealer and they said they didnt feel anything. So I guess I am on my own on this one.

Any ideas?

I have a '92 and it sometimes vibrates/shudders under load around 1800 rpm and it is also driving me crazy. However nothing comes up on the diagnostics and everyone in the car says how smooth it is. But something is not right.....

I suspect its either the engine mounts (tranny mount refreshed but original engine mounts still working at 162Kmiles) or ignition wires/dizzy/coils or my slightly leaking EGR pipe or maybe the O2 sensors. The cost of fixing these is not worth it for me so I keep running it as is with the minor irritation. However I will do a valve clearance and compression check once the weather gets better (in the UK thats unlikely to happen!) and try and fix the egr. Maybe yours is similar?

I have had the car a year and its not gotten any worse, which makes me think its only the ECU ranging the advance on the ignition. When it is under load it can detect detonation and pulls back the advance curve accordingly.

I think it just might be normal, however I can detect a faint uneven tremble in the idle, especially when in drive and parked up a slight incline. Comes through the pedal and the shifting stick. However when my wife is in the car and I feel the engine block with my hand, its smooth as silk. A complete mystery. I have felt other engines from the same generation and its no different. One guy thought I was a complete freak for wanting to "touch his engine", another was a taxi driver who said mine was running perfect. His had 240Kmiles.

A lexus tech who I questioned said the crank sensor lead can sometimes get worn and this can cause the problem, but mine is fine.

Good luck!

[Sweet95LS400]

Mine isnt a hesitation or stumbling, it feels like its comming from the rear end. Are their any bushings or mounts for the rear end or drive shaft that could need replacing? I am guessing its just a mount getting soft and changing the drive line angle just enough to get some vibration under load.

[pachocco1]

The are the rear differential bushings, rear sub-frame bushings, and others I am probably missing.

Why are you certain it is drive shaft related? With your symptoms, I would look at a imbalanced wheel ( maybe you lost a weight) or a rim out of true (hit any curbs or really big pot holes lately).

[Sweet95LS400]

The reason I think it is driveshaft related is because the vibration only happens under heavy load or hard acceleration. If you are accelerating hard and then quickly leave off of the pedal it immediately goes away. If it were a tire out of balance or wheel out of round it would still be there. Plus I have had the tires balanced and rotated and there is no change.

[nc211]

We have the same car and gremlins...just came back from the beach...mine has this too "still..damnit" and it is definetly in the driveline! I just had the car aligned and balanced at the dealership, so it's not the tires. Plus, all the time the dealership had mine over the wobble, I know the rims are ok too. But how I KNOW it's in the driveline is due to those flex-couplings I messed with a few weeks back....

If you recall, I bought some ebay ones, and had them put on. A few days later when I was finally able to hit the highway, I noticed a very fast vibration matched with a very low rumble noise from the rear of the car. I took the car back to the indi-shop and had the old ones put back on. Well, going against my last post in my thread about the flex-couplings, Now I'm not so sure the ebay ones are bad. Because my car is now doing that again, just not as badly. It's very noticable, it's in your seat bottom, and it's from the rear. Here is what I think is the problem:

1) My guess is the 6 bolts that match the shaft to the differential are torque spected. I think my indi-shop did not use correct torque specs when tightening the bolts "some at 20lb's, some at 25lb's." This would cause a misalignment probably...

2) There are 3 mounts for the rear differential. Two are on the rear and are rubber insulated...Mine are new. But the third is on the passenger side and mounts the differential up to the bottom of the car. I have a feeling they are rubber insulated as well....Mine is original.

3) When I turn the rear section of the driveshaft by hand, there is about a 1/2 inch play. When I turn the front section of the driveshaft, there is NO play. This makes me think it's somewhere in the spider bearing section of the shaft "the center section where they both meet." I am wondering if the indi-shop did not damage this when they replaced the flex-couplings to begin with. I bet they dropped the rear shaft, let it hang for a few minutes, then reattached it. This could have possible put so much weight on the center-bearing section that something was bent. Either way, Sweet, I stand behind you 110% on this one...It is in the shaft....

I will know more later. I am going to reinstall the ebay coupling on the rear of the car myself, and make sure the torque settings are perfect...will report back later...

[sonyman]

It is possible for the driveshaft to go out of balance. My old SC400's driveshaft was out of balance and the car had a similar issue where it would vibrate at highways speeds. If it's the driveshaft a good shop may be able to see it vibrating by jacking up the rear of the car and accelerating it freewheel. It may be something else that they'll see by jacking up the back end of the car. Lexus technicians are actually able to pinpoint vibrations to the exact component using sophisticated sensors and diagnostic tools, but that's at least $100 for the diagnosis. It might be worth it though.

Offtopic- nc211, could you shoot me your email address by chance? I've got a little problem I'd like to ask you about but I can't PM you (<20 posts).

Scott

[pachocco1]

The reason I think it is driveshaft related is because the vibration only happens under heavy load or hard acceleration. If you are accelerating hard and then quickly leave off of the pedal it immediately goes away. If it were a tire out of balance or wheel out of round it would still be there. Plus I have had the tires balanced and rotated and there is no change.

I understand completely!

Here is what I replaced and why.

I also replaced the driveshaft. In the end, the car was perfect, but my wallet a good deal slimmer. Ultimately, my car got totaled soon after.

Best of luck.

[nc211]

It is possible for the driveshaft to go out of balance. My old SC400's driveshaft was out of balance and the car had a similar issue where it would vibrate at highways speeds. If it's the driveshaft a good shop may be able to see it vibrating by jacking up the rear of the car and accelerating it freewheel. It may be something else that they'll see by jacking up the back end of the car. Lexus technicians are actually able to pinpoint vibrations to the exact component using sophisticated sensors and diagnostic tools, but that's at least $100 for the diagnosis. It might be worth it though.

Offtopic- nc211, could you shoot me your email address by chance? I've got a little problem I'd like to ask you about but I can't PM you (<20 posts).

Scott

Scott, I typically won't post up my email address in the general forums. Under my profile, do you see the option to "send email to member"? You should beable to do that function?? Or if you don't mind, create a junk email on yahoo or something like that, post it up, and I"ll respond from my email..

[Sweet95LS400]

I took it to the dealer and they said they can't feel anything. I think they just don't know what it is.

[nc211]

I took it to the dealer and they said they can't feel anything. I think they just don't know what it is.

Now is the time to send a polite email to the sevice center and request the senior tech go for a ride with you as well. Not to knock Lexus service centers, but they usually asign these types of problems to the "new guy" who 99% of the time thinks it the wheels. Go for the senior tech only at this point. Make friends with him, and tell him he can have the car for as long as he wants. They'll find the problem.

[sonyman]

I took it to the dealer and they said they can't feel anything. I think they just don't know what it is.

Now is the time to send a polite email to the sevice center and request the senior tech go for a ride with you as well. Not to knock Lexus service centers, but they usually asign these types of problems to the "new guy" who 99% of the time thinks it the wheels. Go for the senior tech only at this point. Make friends with him, and tell him he can have the car for as long as he wants. They'll find the problem.

Exactly. With my old car I purposefully chose the technician from Johnson Lexus who had been there for the longest time. He was more familiar with the car's issues than the other techs who were fresh out of training.

nc211--What I meant was for you to PM me with your email address if possible, since I can receive yet not send.

Scott

[nc211]

Sony, you can't receive them either. I get this error...

"This message can not be sent because the recipient has their personal messenger disabled or their personal messenger inbox is full.

This personal message has not been sent"

May I ask...is that tech you use at Johnson a very tall man? I refer to him as God, because if it is him you use, you are in the hands of a LS400 God. You have to trust a tech who owns LS400's personally as well... His initials are D.M.

I took it to the dealer and they said they can't feel anything. I think they just don't know what it is.

Now is the time to send a polite email to the sevice center and request the senior tech go for a ride with you as well. Not to knock Lexus service centers, but they usually asign these types of problems to the "new guy" who 99% of the time thinks it the wheels. Go for the senior tech only at this point. Make friends with him, and tell him he can have the car for as long as he wants. They'll find the problem.

Exactly. With my old car I purposefully chose the technician from Johnson Lexus who had been there for the longest time. He was more familiar with the car's issues than the other techs who were fresh out of training.

nc211--What I meant was for you to PM me with your email address if possible, since I can receive yet not send.

Scott

[sonyman]

His name was Lynwood (sp?).

Scott

[branshew]

If it were a tire out of balance or wheel out of round it would still be there. Plus I have had the tires balanced and rotated and there is no change.

A wheel out of round would be there at all times, but not necessarily a tire out of balance. Vibration from a tire out of balance can happen at certain speeds and not at others. When mine were out of balance it was only between 60-68 MPH that I noticed any vibration/wobble.

Do you notice it at certain engine RPMs or only at certain speeds regardless of RPMs?

[pachocco1]

I took it to the dealer and they said they can't feel anything. I think they just don't know what it is.

Did you reference the TSI? (the link in my past post)

DATE: APRIL 26,1996

LS 400 DRIVESHAFT & DIFFERENTIAL MOUNT CHANGES Page 1 of 1

For improved driving smoothness when accelerating from approximately 35 m.p.h., the following production

changes have been made:

1. Rear drive shafts phase–matched between inboard and outboard joints.

2. Dynamic spring constant of differential rear mount changed.

3. Dynamic damper added to stabilizer bracket.

PART NUMBER INFORMATION:

REF: DRIVELINE/

DIFFERENTIAL

NO: DL002–96

MODEL: LS 400

PRODUCTION EFFECTIVE:

Starting VIN: JT8BH22F#T0036670

[sonyman]

I took it to the dealer and they said they can't feel anything. I think they just don't know what it is.

Did you reference the TSI? (the link in my past post)

DATE: APRIL 26,1996

LS 400 DRIVESHAFT & DIFFERENTIAL MOUNT CHANGES Page 1 of 1

For improved driving smoothness when accelerating from approximately 35 m.p.h., the following production

changes have been made:

1. Rear drive shafts phase–matched between inboard and outboard joints.

2. Dynamic spring constant of differential rear mount changed.

3. Dynamic damper added to stabilizer bracket.

PART NUMBER INFORMATION:

REF: DRIVELINE/

DIFFERENTIAL

NO: DL002–96

MODEL: LS 400

PRODUCTION EFFECTIVE:

Starting VIN: JT8BH22F#T0036670

Did they change the mounts mid-production? That vin doesn't look like mine (2nd gen). I know they revised them when they redesigned the LS400 for '95.

nc211-can you pm me on clublexus with your email or perhaps phone #? I'd like to contact you asap as I've already contacted lexus corporate in regards to the driveability improvement.

Scott

[nc211]

Sony, I sent you a pm over there.

The main source of driveline vibration pertaining to that TSB is the driver's side differential mounting bushing. If you look under the car, from the rear on the back of the differential, you will see two donut sized black mounts sticking out the back of the crossmember. These are the two mounting cushions for the differential. The way the prop shaft spins, it puts most of the torque on the driver's side cushion. You can start the car, apply the e-brake "MAKE SURE IT HOLDS GOOD", put the car in drive, get out, and look up under the rear at the cushion. If you see the rubber is split, then it's time to replace it. I had to replace mine a long time ago, and it helped.

Now if I could just stop fartin' around with my car, maybe I would stop !Removed! it up!

[W201 sweden]

The same "drivetrain vibration during acceleration and heavy load" gremlin lives in my -95 LS too... :(

I have not started trouble shooting yet, but I will get back with whatever findings I make.

For what it's worth - on the W210 Mercedes E-class with the 2.4 V6, the prop shaft was too weak.

We had some owners that complained about symptoms similar to what we are dealing with here, and we tried "everything".

At last we swapped the prop shaft, and put in the thicker one used in W210 3.2 V6.

Tada, problem gone.

Over engineered Mercedes Benz - my a**... ;)

/Alexander from Sweden

[Leadfoot]

post withdrawn after reading the thread more carefully. soz.

[oohryry]

I do recall a couple of years ago I had a problem with harsh vibration at highway speeds. Had an alignment and it still didn't solve the problem. Took it to a tire place and they told me that two of my tires were broke. What in hell does that mean? He told me the steel belts were broken and I needed two new tires. Well I listened and what do you know, problem was solved. Not saying this will solve your problem, but something for everyone to think about that may be ignorant to the fact like I was that tires get broken.

[nc211]

I went through the tire thing a few months ago, ended up with a new set of Michelins. This is definetly in the driveshaft area, towards the rear around the differential. If it's not raining this Sunday, I'm going to get under the car with the air wratchet and check some things out...