Vansibel

So far, the Lexus have been pretty problem free, so I guess I can't help but notice the small stuff. Has any ls600 owner noticed a small vibration/shudder when they decelerate (without braking) on the highway ? It may be only a hybrid issue even during normal operation as the electric engine are recharging the battery. Any though or similar experience ?

riknchar

I can't recall ever experiencing what you're describing. I do get a very slight vibration when I'm sitting still and the engine kicks on or off, but nothing that I've felt while actually traveling at highway speeds.

hfahmy

Did you get the AWD drive train TSB L-SB-0023-11 done?

caha14

Short answer, yes! It is entirely separate from the TSIB for the transfer case for shudder when turning.

I was actually going to start a thread about this, but since I've had the car for only a few months, I've been "gathering data" for a while.

In my case, the issue seems intermittent, not in its presence (i.e., there is always some shudder, even if slight) but in its intensity. Sometimes it's tolerable; other times it gets to be annoying.

Indeed, it occurs during regenerative braking, as soon as you see the power meter go into the "Chg" zone upon letting go of the accelerator (or applying the brakes). At its worst, it can feel like a bad case of warped rotors, except it isn't the rotors.

One thing I've noticed, is that the issue surfaces when the engine is on. As the vehicle slows down (and shudders), the moment the engine turns off, the shudder virtually disappears. It's almost as if in this state, the engine is "fighting" the rest of the drivetrain.

Similarly, when I am merging into heavy traffic, letting go of the brake as the engine revs around 1000+ rpm, the car can feel jerky. If the engine is off, it's smooth as glass, again making it seem as if the engine is fighting the drivetrain.

My dealer has experienced the issue, and I opened a case with Lexus and drove the car with a Field Technical Specialist. Detailed driving snapshots of relevant parameters were sent to Lexus engineers, and so far, nothing unusual has been found. Problem is that this car is so rare, that there is nothing on the lot to compare it to. Thus, in my situation, unless something really goes wrong with the car, the next step will be to find another car to compare to and take it from there.

While this could, unfortunately, turn out to be a "characteristic" of the car (though based on others' responses, it doesn't sound like it is), I would be hard-pressed to think that it is normal. I had never owned a 600 before, but have driven plenty of RX450hs, and while they are different animals, at the end of the day, I don't see why the "flagship" would be so noticeably less smooth under regenerative braking.

CJITTY

There was a TSB on vibrations, usually generated during u turns or other hard turns that I noticed my car had repaired prior to me purchasing it..but at highway speeds, if I let off the gas there is no shuddering going on that I can tell. I'm running 22x9 front and 22x10.5 wheels also. Actually, if I coast long enough the gas 5.0 shuts off completely. There is one part of my commute that is essentially down hill. After about a 1/4 mile, the engine appears to shut off as I see the RPM gauge fall down.

Vansibel

Exactly, this is pretty tricky because it's intermittent. Sometime I don't feel anything at all, but sometime it's very noticeable, especially during the first moment of the day that I take the car. This is the reason why I thought it was the electric motor recharging. When it decelerate I can feel some kind of engine braking, as if the brake were slightly applied when in reality I'm not braking. But I'm definitely feeling resistance in the car and this is what appear to generate the shudder.

caha14

Right, I actually first learned of that issue when you got your 600. Mine already has the updated transfer case fluid from the factory (I checked the VIN vs. the range on the TSIB before I signed!).

This is helpful to know, thank you. Thus far, it seems like this shudder does not affect every car equally. My car will shudder (sometimes quite noticeably) during deceleration, and the moment the 5.0 shuts off, smoothness returns, even while under regenerative braking.

Yes, and just today when exiting the highway, the regenerative braking felt like a severe case of warped rotors, only for me to speed up again and feel almost nothing the next time I slowed down. To date, I have found no correlation to ambient temperature, engine temperature or charge level of the hybrid batteries. Ambient and engine temperature only factor in to the extent they keep the 5.0 on for longer, as it seems like it's the mix of the regenerative braking and gas engine that makes the shudder "shine".

Never felt this on any other hybrid... My case with Lexus is still open; the plan is to track down a car to compare to, as I mentioned before, but it is certainly most helpful to hear of others' experiences here. As I said, the parameters from my car that Lexus hybrid gurus in CA have reviewed seem ok, but if there is something else (mechanical, perhaps) going on, I don't know that these parameters would necessarily capture it. At the end of the day, this does not seem normal, and I wonder how many more owners report the same as CJITTY: no shudder.

Vansibel

What might help to identify the problem would be to include our car trim (as it may be related to a specific feature/option on the car). I was about to say also weather condition but from your testing it doesn't seems to be related.

Mine is a 2008 ls600hl executive 4 seat (with apcs/driver attention monitor system) - canadian car.

wanderer99

Yes - I have this on my 2009 LS600 to a degree as well. In my case it happens when coasting down from 70MPH or similar on a fairly flat or very slight downhill surface, not on a steep descending grade. It does feel like the engine is fighting with the battery charging system and it's almost like an on-off-on-off slight stutter effect as you coast down in speed.

I had this issue to some degree a year ago which started shortly after I bought my car. I put it down to the fact that the engine was probably run on cheap fuel by the previous owner so put through a few bottles of Techron over a few tanks of gas. This helped and really smoothed out the engine, so I thought that was probably the issue. It's been OK over the summer months but now that it's cold and we're on the winter fuel mix again.... it's back.

I started the Techron thing again a week or so ago and already the car is definitely smoother. I'll do a third tank in the next week or so and report back if it makes any difference in my case.

caha14

Same car more or less, though no executive. APCS and Premium Luxury Package II.

This is interesting. I have had positive results with Techron, though I would have never imagined using it in this particular situation (especially since I just crossed 11k miles).

My engine is generally fairly smooth, and the issue feels more like the engine is refusing to "disengage" from the driveline during braking (you know, as if some electronic clutch is not fully releasing - not that this driveline is as simple!).

However, given your experience, I will give it a shot. Thank you for sharing. I'm very curious to see what will happen, and guess what I have a brand new bottle of in my garage at the moment...

I used to put it in my 460L all the time to deal with idle issues.

Vansibel

Was wondering if you ever got this resolve since you seemed to be involved with Lexus. Mine still vibrating during deceleration but I also noticed the same kind of vibration although less intense between 60-80 when cruising or accelerating (over those speed car is smoother again). I noticed this lately because I have been on a newly constructed part of the highway near where I live and since there is no road imperfection I can definitely feel the vibration when I'm on this part of the highway. So in the end although the worse is when decelerating the problem is still there when just cruising. Its very hard to diagnose because it seems to be intermittent and sometime worse than other. Tried to put on neutral while cruising but the vibration is still there. Serviced my car lately for spark plug replacement, brake and transmission (hybrid transaxle) fluid but didn't make any difference. Have two set of wheel and tires and both does that. Very annoying as the car is smooth as butter the other time. But as soon as I hit the highway I have this issue. I can't be sure but I have a hard time explaining this on something else that a mechanical part that would sometime engage and disengage, like for example one of the electric motor. Had done the transfer case fluid replacement and differential last year (not part of any TSIB though). Also car have always been serviced with Toyota 0-20 synthetic oil. I could go to the dealer but from my past experience they will be clueless for this kind of issue and they might damage my car and try to hide it again.

Vansibel

Just stumbled on that thread, people with AWD ls 460 seems to have similar symptom: https://www.clublexus.com/forums/ls-...n-problem.html

Tec80

Here's what I think the issue is:
As the car ages, the rubber cushions in both the transmission mount and the rear differential nose mount sag downward slightly (1-3mm), which gradually puts them out of parallel to each other. This causes driveline vibrations exactly like what you guys are describing.

Here is an exaggerated illustration of the sagging described above, and what it does to angular alignment of trans output & diff. pinion:


Here is the LS460 rear differential mount exploded view, there is a selective washer 41653A marked in green that is available in 3 different thicknesses, 1.0, 1.6, and 2.0mm. This washer goes between the top part of the differential mount cushions and the frame. Thinner 41653A washers move the pinion nose up, which is needed to eliminate the misalignment-induced driveshaft vibration that occurs when coasting:
Part numbers for 41653A:
1.0mm washer: 9020115020
1.6mm washer: 9020115028
2.0mm washer: 9020115021

caha14

Funny you mention this, as I am actually in the midst of following up. I have re-re-opened the case, and they are back to searching for a car. Because I have a '10, they are looking for a '10-12 car, which is even more of a unicorn here on the east coast.

I am not sure that is the same issue (on the 460 AWD) as on my 600. I wonder, Vansibel, if we have the exact same issue. At any rate, I had read about the front shaft issue a long time ago and intended to raise it for consideration, just in case (in the spirit of connecting dots) - thanks for bringing it up (nice reminder!).

Very helpful and interesting info, Tec80. This reminds me of a part of the work that was done to my 460 to exorcise all the vibration demons. I am not sure it's applicable, though again, it's another factor to consider.

In my case, I either need to be braking or coasting for there to be shudder. When coasting, the fore-and-aft shudder coincides with the needle going to "charge". The second I shift to N, the car can't recover energy anymore, and the shudder disappears. FWIW, service brakes are also out of the equation (i.e., if I brake in N, braking is perfectly smooth).

So, basically, there needs to be a load on the driveline (negative torque, specifically) for there to be shudder. Remove that load, and everything is fine. The sagging you describe seems like it would trigger vibration under any/no load. Am I missing something?

Tec80

Negative torque (car pushing the engine or wheels driving the engine) will cause the nose of the pinion to rotate downward, compressing the lower forward diff mounting cushions. If the cushions are already allowing the diff nose to sag down in the static state, the load from deceleration will make it sag further, putting it out of parallel with the transfer case rear driveshaft output. Anything past 1 degree out of parallel and you will begin to feel the vibration from the driveshaft accelerating and decelerating as it turns.

This is the opposite of axle windup under acceleration. When accelerating, the rear wheel torque creates an equal but opposite force on the diff housing, trying to rotate it backwards (nose up). The cushions prevent this. But, if the nose was too high in the static state, you'd feel vibration on acceleration as the diff nose moves up and puts the system out of parallel.