lucyq

This Thread is for the following issue: An unacceptable hesitation in transmission downshift/passing gear/kick-down (while the vehicle is in motion). This is an important issue for those who experience it (for example, see the 2 NHTSA complaints from actual LS460 owners below in Footnote 1). It should not be closed as long as LS460 owners experience this issue and desire to learn about how to resolve it.

"Tee" recently closed my proposed thread about this ( https://www.clublexus.com/forums/ls4...esitation.html ), incorrectly stating that "This has been discussed several times over the years, here is the link found in the FAQ sticky located at the top of the LS460 forum. https://www.clublexus.com/forums/ls4...-problems.html ". However, it is clear that the link he provides is for a different thread about poor acceleration from a stop (due to an engine timing issue). (Nospinzone also suggests this topic has been discussed in Club Lexus Forum, but does not provide a link to the thread that he is referring to.)

Please don't close this Thread, as I have not been able to find a Thread on this Club Lexus Forum that specifically addresses the issue I now describe to you:

I have been trying to wrap my head around my 2008 Lexus LS460’s transmission downshift (or “kick-down”) hesitation for some time. Not only does it hesitate to downshift into a lower passing gear, after the downshift and acceleration does occur, when I lift my foot to stop the acceleration after I pass, the transmission remains in the passing gear and hesitates to upshift (leaving the engine revving in the lower gear) for an unacceptable time. It does eventually downshift to a passing gear and upshift out of the passing gear, but it is dangerous. For example, I start crossing into the passing lane in expectation of rapid acceleration, but the car's hesitation to accelerate as expected places me at risk of being hit from behind.

Seeing the NHTSA complaints from other owners [see Footnote 1 below] gives me hope that Lexus has a fix for it. Lexus owners are not the only people who have experienced the same problem. For example, Jay Shoemaker, in his November 13, 2006 article on the Lexus LS460 (titled “Lexus LS 460 Review”), described the delay in downshift as follows: “there's an unacceptable hesitation as the transmission rows through a few gear changes before finding the meaty part of the engine’s torque range” (http://www.thetruthaboutcars.com/2006/11/lexus-ls-460/ ). My take on this “unacceptable hesitation” is it reflects a software programming issue.

Regardless of the number of gears a transmission has, a rapid depression of the accelerator pedal by a given distance (of pedal travel) should cause the computer to rapidly select a gear to downshift to and make it happen quickly (based on the computer program that takes into account the rate of pedal depression, the distance of pedal travel, and the speed of the car). The transmission should downshift to that selected gear almost instantaneously given today’s fast computers, regardless of the power created by the engine (i.e., regardless of what the variable valve timing (VVT) and direct injection (DI) programs are doing).

Has anyone else experienced this downshift hesitation issue? Is there a Lexus Technician out there who can explain why this occurs and how it can be solved? Is there a Service Bulletin with an official fix?

------------------------------------------------
Footnote [1]:

“THE CAR WILL (INTERMITTENTLY) HESITATE TO ACCELERATE. THIS IS ESPECIALLY DANGEROUS WHEN YOU ARE TRYING TO MERGE INTO THE FREEWAY OR SIMILAR OCCASIONS. WHEN ATTEMPTED TO DEPRESS THE GAS PEDAL WITH EXPECTATION THAT THE CAR WILL RESPOND AND ACCELERATE AS NORMAL, THE ENGINE JUST REVS UP AND THE VEHICLE DOESN'T MOVE ANY FASTER THAN CURRENT SPEED. THIS WILL CONTINUE FOR 5-10 SECONDS THEN IT KICKS IN. THIS DELAYS IS VERY DANGEROUS WHEN YOU WANT TO GET OUT OF HARMS WAY (ACCELERATE TO MERGE INTO FREEWAY, PASSING ETC). THE PROBLEM IS INTERMITTENT AND WILL GO AWAY BY ITSELF WITHIN A FEW HUNDRED MILES (BUT WILL COME BACK SPORADICALLY). ALL THIS HAPPENS BY ITSELF AND CANNOT BE REPRODUCE AT WILL” (NHTSA ID Number: 10507520, Date Complaint Filed: 04/08/2013).

“WHEN I NEEDED TO PASS A VEHICLE, I WOULD STEP ON THE GAS (MOST OF THE TIME PUSHING THE ACCELERATOR PEDAL TO THE FLOOR) THE CAR WAS VERY SLUGGISH AND UNRESPONSIVE. IT WOULD TAKE ABOUT 10 SECONDS FOR THE VEHICLE TO SLOWLY ACCELERATE AND THEN THE CAR WOULD TAKE OFF WITH THE RPMS CLIMBING NEAR RED LINE UNTIL I RELEASED MY FOOT OFF THE ACCELERATOR” (NHTSA ID Number: 10506001, Date Complaint Filed: 04/11/2013).

Bozookah

You know what, I am experiencing the same issues plus some more, let me know if you have any symptoms like mine. Here is the thread I posted up today https://www.clublexus.com/forums/ls4...-problems.html

ta1972

iTrader: (1)

If all your suspension and others checks out good, then it's most likely a ecu software issue. Probably needs to update the ecu software or replace.

lucyq

At about 85K miles, I convinced our Lexus service department that they ARE able to change the transmission fluid, which I proved to them by showing them the service procedure (which I found on the internet). Cost me $150 for this. This solved the problem -- what a dramatic difference the transmission fluid change makes!

Problem starting again about 6 months later (don't get me wrong, transmission shifts, and in general performs, like new WHEN IT DOES SHIFT CORRECTLY).

Service department suggested a reflash the ECU, which has worked so far (it has been about 6 months since reflash; car has about 93K miles now).

Cannot tell you if, or when, the shift hesitation will begin again.

Peter.

mdpresco

Did they change ALL the fluid or just drop the pan and refill? My Toyota dealer wants $350 to change all the fluid.

7milesout

Attempting to make an automatic transmission do what you say is the target of EVERY SINGLE DRIVETRAIN engineer (that works on automatics) on this planet. But when you mix software with hardware, unfortunately real life results. Meaning, it's not like when I want a P to show up on the screen, so I press P and it pops right up there. An automatic transmission is a VERY complex piece of machinery, throw 8 speeds into it, and it is ri-DONK-u-lously complex. When the accelerator pedal signal changes rapidly, you can bet the computer is quick to react. But for a slushy automatic transmission to jump from 8th gear, to 2nd gear will never be lightning quick. I've always said that anything over 5 speeds should just go to CVT. The 600h is proof that its a good idea. Those guys talk about instant torque when they hammer down ... and I believe them. The industry has been driven to program a car to LOW Low low rpm as much as possible. So when cruising and easy on the throttle at 40 mph, the 460 might be in 8th gear. Stomping on it could realistically require 2nd gear. It's going to take time.

My car does this as well. It's irked me a time or two. But most of the time, I plan WELL ahead, and if I see such a circumstance possibly arising, I pull the shifter over into manual and get it in an appropriate gear. When I step on it then, there is 0 time to shift, and it GOES!

Imagine you driving along with an 8 speed manual transmission, along at 45 mph, and you're in 8th gear. And then out of the blue, your passenger leans over and screams in your ear, "GO TO 2ND!!! GO TO 2ND!!! GO!!! GO!!! GO!!!" Ok, that's just a funny thing to think about, not exactly related. But imagining this situation, and scaring the crap out of the driver, I think it might take 10 senconds to grab the gear, shove the clutch, and find 2nd with someone yelling in your ear!

I have to say, having been an automotive design engineer, your statement is made as if what you state is not obvious. And that engineers should have just made this transmission shift instantaneously in the first place (as if it is so simple). It stated in such a way is a bit annoying to be honest.


7milesout

DiggerJim

It's true, it's true! I love how I press and go fast and faster and faster. The 600 is the first CVT car I've owned and I love that. The SC isn't a slouch for my driving style but it is noticeably different than the 600's CVT tranny.

superdenso

Try changing the transmission fluid 3x, with at least 50 miles in between.

Trumpanche

When my engine hesitation issues act up, I get lousy jerky shifts with poor downshift performance. I'd bet you a nickel that what you think is a transmission problem may be the same hesitation issue so many of us have experienced. It comes and goes depending (for me) on how I drive the car and I'm fairly competently keeping it at bay. RoadFrog thought his was licked with a change in engine oil but even his creeped up again recently before disappearing again. One thing that's interesting in these newer cars is that transmission shift points directly affect the engine's timing (retards it to reduce torque and smooth out the shift). So when the timing is already being retarded because of the engine issue and the engine is putting out the torque the tranny expects, the shifting is going to be yucky. Good luck and keep us updated on your progress!

Lextek84

From the way this problem is being described it sounds to me like your ect is downshifting properly however you are having an engine performance issue due to a low knock correction feedback value i.e. Your ecu is retarding your timing because it may be detecting knock in your engine this could be due to low quality fuel and believe me you can buy premium that is crappy and your car won't like it. My recommendation is try a different gas station to start then slowly start beating the bricks out of your car I mean full throttle acceleration as often as possible and see how it responds. There is also the possibility you may need some new spark plugs they are recommended to be replaced every 60k. The 07 and 08 have an Ecu reflash for hesitation issues. However if after all that you are still experiencing this issue there is the possibility for an actual mechanical issue that is causing your knock values to be low.