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Discussion Starter #1
Since I bought the car the power train has performed poorly. There was a long break in period with the adaptive 8 speed transmission. At 5-600 miles I took it to the dealer and a tech and service rep rode in the car. They told me the performance I experienced was from the 8 speed transmission.
Every time I take it to the dealer for maintenance I tell them it is our 7th minivan and by far it performs the worst of all of them. A couple of months ago I was in for service and they said they would contact corporate who I had to contact. Corporate tells me to take it to another dealer which would be two hours from us.
The car feels like it has a dead miss sometimes between 25 and 40 mph. Our neighborhood has a strict 25 mph speed limit and the car is quite annoying. The poor performance is also intermittent so I think it is correctable.
Over the years I have rebuilt GM Quadrajet carburetors, replaced plugs, points, condensers, water pumps, radiators, hoses, belts, and heater cores.
I still do my own brake and rotor replacements. I will do my own oil changes if necessary.
This is our second Sienna and the 2015 performed much better than our current car.
 

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i think the 8 speed is a touch clunky myself. it is always shifting. putting the trans into power mode is part of my startp procedure. but, even so it always is shifting too much. this of course, is my opinion. it is great on the highway, which is most of my driving with my sienna, so i will deal with it. good luck finding a solution.
 

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Discussion Starter #3
The transmission shifts smoothly and is probably relatively efficient. The first or second gears rev too high for my liking, but that is not my complaint. I think a close ratio 8 or 9 speed would be better than the wide gear ratios they use.
My main complaint is the bucking sensation of an engine misfire I get between 25 and 35 to 40 mph. It is the same sensation a driver gets when driving stick when he is pushing the accelerator in 4th gear at low speed when he forgot to downshift to second gear. The car feels like it is in the wrong gear or the torque converter is prematurely locking up. I would be willing to bet that there is a problem with the software that controls the drive train.
 

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I do not think it is a problem with the software, but instead it is by design. The purpose of the 8 speed was for maximizing fuel economy, and in doing so, the transmission is designed to be in the highest gear at the lowest speed possible. This is what happens and the transmission is programmed to shift into the highest gear possible at 25 mph (4th gear) when there is not heavy throttle, thus the gear is right on the verge of engine lugging. This can be addressed by turning ECT on, which alters the shift points and gear selection based on remapped throttle input and you can eliminate/reduce this effect. It is all done in the name of fuel economy. I also currently have a 2015 and a 2011 as well with the 6 spd and yes, those shift smoother and are also gear much better closer together and the programming is so that the feel is much preferred over the 8 spd. However, I also find that now ( with 2100 miles) my 8 spd is much better and has probably learned my driving habits and is behaving much more so like the 6 spd. I no longer turn on ECT anymore and the transmission now feels and shifts fine, but it could also be that I am now used to the new shift points.
 

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I brought my 2018 Limited FWD to the dealership for an ECU update. After 2-3 weeks of driving the transmission is back again to being sluggish. It’s like always finding the right gear. I do city driving most of the time and it really sucks.
 

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Discussion Starter #6
I do not think it is a problem with the software, but instead it is by design. The purpose of the 8 speed was for maximizing fuel economy, and in doing so, the transmission is designed to be in the highest gear at the lowest speed possible. This is what happens and the transmission is programmed to shift into the highest gear possible at 25 mph (4th gear) when there is not heavy throttle, thus the gear is right on the verge of engine lugging. This can be addressed by turning ECT on, which alters the shift points and gear selection based on remapped throttle input and you can eliminate/reduce this effect. It is all done in the name of fuel economy. I also currently have a 2015 and a 2011 as well with the 6 spd and yes, those shift smoother and are also gear much better closer together and the programming is so that the feel is much preferred over the 8 spd. However, I also find that now ( with 2100 miles) my 8 spd is much better and has probably learned my driving habits and is behaving much more so like the 6 spd. I no longer turn on ECT anymore and the transmission now feels and shifts fine, but it could also be that I am now used to the new shift points.
Thanks for your insight Hangman. I agree with your assessment of the trans being in the highest gear. What's interesting is that the problem is sporadic. The last few days the car has been performing relatively well. That's why I think it is an intermittent problem which is fixable if they can figure out where the problem is. When the car is really acting poorly I have felt the problem occurring shortly after start up. Approaching the stop sign ten feet from our drive way the car almost comes to a stop without applying the brake, I have felt the sensation on acceleration and the car upshifts with the condition continuing. If the car drives like it has been for the last few days I will be happy. Our odometer just crossed 10,000 miles. I had turned on the ECT at different times and it did not seem to make any difference.
 

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That is interesting if you have turned on ECT and it doesn’t make any difference. In that case, I think there may be some issue, as I have never experienced that with ECT turned on, although I only have real low miles thus far.
 

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Discussion Starter #8
That is interesting if you have turned on ECT and it doesn’t make any difference. In that case, I think there may be some issue, as I have never experienced that with ECT turned on, although I only have real low miles thus far.
It's been awhile that I have turned on ECT. I will try it again if I remember. Again, I appreciate your feedback. Toyota has been almost no help. I complain to the dealer every time I bring it in for service. They find nothing and the service writer tells me that Toyota is aware of it. Toyota corporate tells me to go to another dealer which would be a 2 hour ride. Nothing like going in a circle and getting no where.
It's been interesting on this site that I have not seen other complaints. That's why I think my car is abnormal with a fixable problem.
 

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I have had very similar issues with my wife's 18 Sienna limited. The bucking sensation has happened a few times, but the dead pedal thing drives me nuts. We have brought it back to the dealership three times, and even demonstrated the bucking at 40mph, but have been told it is "operating as designed" every time. We have had a Toyota trouble call number for three months, no contact. This will most likely be our last new Toyota, and certainly the last sienna.
 

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Seahawkdoge, thanks for your reply. Misery loves company I see. It is nice to know that your car has about the same problem as mine. Please explain the dead pedal thing to me. That is a new one for me.
My personal feeling is that Toyota knows what my problem is and cannot fix it. That is why they are stone walling it. The car probably performs as designed. The design they came up with was a poor excuse for a so called premium automobile. Two of my friends here have Chrysler Pacificas. Their performance with an 8 speed transmission is superb and their gas mileage is better. In less than two years we will replace this car. What we buy and recommend will depend on how we are treated. It's interesting that after every interaction with the dealer or corporate I am given a survey to complete. I have given the appropriate questions very poor ratings. I have heard crickets from them in the last few weeks. It's also interesting that this transmission was first used in 2017 and is still being used on the 2020 versions.
 

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What ever you decide to get, stay away from the Odyssey. Just be glad it’s not a Honda Odyssey with a transmission that literally tries to kill you and your family. Getting rid of the POS 2018 Odyssey was the happiest day of car ownership for me, even if I had to take a bath financially to get rid of it. You can read about my experience here.

I am serious when I say that it literally tried to kill my family. We almost got into serious wrecks on at least 5 seperate occasions due to the Ody’s transmission. I bit the bullet financially and got rid of it after 16 months. I just could not risk my family’s well being on the Odyssey. Also, my case was not an isolated incident. The Ody Forum is littered with similar experiences.

 

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Interesting thread. I have been totally happy with my sienna (2018 AWD) so far, and the transmission hasn’t given me any issues like what you are describing. Maybe an occasional slightly rough shift, or occasional early-shift-then-lug situation, but that’s about it.

I sure hope your experience isn’t in my future.
 

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In one respect, this thread is reassuring for me. After my 2002 Sienna died, away from home, I bought a used 2018 FWD which happened to be on the lot of the first dealer visited, in the right color/options. My only hesitancy was that the 2018 had been a fleet rental--so it's my "rescue" minivan.

I, too, have experienced a "shudder" or hesitancy, noticeable on acceleration, in the, roughly (pun intended!), 25 to 45 mph range. I had thought maybe there was drive-line damage, hidden from my initial impression. So, I'm glad the issue isn't unique to my vehicle. Fortunately, I drive the van mostly on the highway, where it performs quite well, and by indication of the computer, achieves around 29mpg.

Will be following this and any related thread!
 

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Sadly enough, we have had both a 2018 Odyssey and Sienna. They both suck, but we took the hit and got rid of the Odyssey after four months. The sienna will most likely be repurchased under lemon law.
Our Odyssey decided to emergency brake twice, once on me and once on my wife. No car in front of us, but I think it reacted to oncoming traffic. The second time happened to my wife with the kids in the van, and she nearly got rear ended. That was enough for us. At least the sienna hasn't tried to kill us, it just sucks.
 

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Oh, and the dead pedal refers to how the first quarter of the gas and brake pedals do basically nothing. Our gas pedal has a specific spot where it goes from doing a little something, to nothing, to a lot of something, in a short space of travel.
 

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Sadly enough, we have had both a 2018 Odyssey and Sienna. They both suck, but we took the hit and got rid of the Odyssey after four months. The sienna will most likely be repurchased under lemon law.
Our Odyssey decided to emergency brake twice, once on me and once on my wife. No car in front of us, but I think it reacted to oncoming traffic. The second time happened to my wife with the kids in the van, and she nearly got rear ended. That was enough for us. At least the sienna hasn't tried to kill us, it just sucks.
Sorry to hear about your problems with the Sienna. We have not experienced any issues yet (knock on wood). Like you, our 2018 Odyssey also emergency braked on me as well, several times on left turns with the other side also making left turns. Almost caused me to get rear ended several times. But the worst thing is the way the transmission tried to kill us.

At a stop sign, or light, we would wait for cars to pass to make a right turn. With cars far away, we would turn right. The van would go in the lane, and then nothing. We would step on the gas, nothing, for about 2 to 3 seconds. The engine would rev, but it acts like its in neutral, then all of a sudden, it would engage the gears and jerk and squeal the tires. Now during those 2 or three seconds, keep in mind you have on coming traffic because we made a right turn. Now 2 or 3 seconds doesn't sound like much, but with cars approaching, trust me, its a scary situation with cars honking at us and such, thinking that we just pulled out and then stopped there for a few seconds. Happened to us a few times. Also, as we were driving highway speeds, I would pass others that are going slow by pressing on the gas pedal to into the left lane when its safe and overtake the car. However, on several occasions, when I do this, it would speed up, as I go into the left lane, then again, feels like the car is stalling or the transmission is in neutral and the car not only does it not speed up, it seems to lose power and slow down. Scary scary scenario, happened to us a few times.

So I took it into the dealer, and their response is, "Yes, we have lots of complaints about this, it's just the way the transmission behaves, and since there's no fix from Honda, we can't do anything about it. They are all like that" I got rid of that POS Ody as I really do feel my family's life was in danger in that car.
 

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Discussion Starter #18
Hangman, that was some story about your O
Interesting thread. I have been totally happy with my sienna (2018 AWD) so far, and the transmission hasn’t given me any issues like what you are describing. Maybe an occasional slightly rough shift, or occasional early-shift-then-lug situation, but that’s about it.

I sure hope your experience isn’t in my future.
Thanks for your input. I'm glad your car works well.
 

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Sorry to hear about your problems with the Sienna. We have not experienced any issues yet (knock on wood). Like you, our 2018 Odyssey also emergency braked on me as well, several times on left turns with the other side also making left turns. Almost caused me to get rear ended several times. But the worst thing is the way the transmission tried to kill us.

At a stop sign, or light, we would wait for cars to pass to make a right turn. With cars far away, we would turn right. The van would go in the lane, and then nothing. We would step on the gas, nothing, for about 2 to 3 seconds. The engine would rev, but it acts like its in neutral, then all of a sudden, it would engage the gears and jerk and squeal the tires. Now during those 2 or three seconds, keep in mind you have on coming traffic because we made a right turn. Now 2 or 3 seconds doesn't sound like much, but with cars approaching, trust me, its a scary situation with cars honking at us and such, thinking that we just pulled out and then stopped there for a few seconds. Happened to us a few times. Also, as we were driving highway speeds, I would pass others that are going slow by pressing on the gas pedal to into the left lane when its safe and overtake the car. However, on several occasions, when I do this, it would speed up, as I go into the left lane, then again, feels like the car is stalling or the transmission is in neutral and the car not only does it not speed up, it seems to lose power and slow down. Scary scary scenario, happened to us a few times.

So I took it into the dealer, and their response is, "Yes, we have lots of complaints about this, it's just the way the transmission behaves, and since there's no fix from Honda, we can't do anything about it. They are all like that" I got rid of that POS Ody as I really do feel my family's life was in danger in that car.
The Service manager of our Honda dealership literally walked out and left the building as I was driving in. He looked at me and walked out. And he never returned a single phone call. The service department told us there was no problem, and just blew us off repeatedly. Three months of back and forth with Honda and the dealer, and I never spoke to the service manager.

We traded in a 2015 Odyssey that we loved, and have had bad luck since.
 

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I had a '17 with the tranny that needed the software fix, and it drove much better afterward. I'm in a '19 now, and my tranny is clunky (as was the '17's) if I let off the gas then reapply. The pedal is a little weird in that it does seem to react a bit unpredictably, but fortunately those two issues (+ why can't I see if the AC is on or off when I start the car until I cycle the button? I miss the old AC buttons w/ a light in them) are minor to me and it's otherwise is an amazing car to me given the performance, quiet comfort, and probable reliability.

If you're unhappy with a Toyota dealer and are considering other brands, please check their forums, especially Chrysler's.

It's sad to me that a great automobile can be tarnished by the very people who profit from the sale - we pay their paychecks, and I certainly have concerns about dealers, which is why I see an independent mechanic I've gone to for years (even for the maintenance that Toyota would do for free). Trust is HUGE w/ my rides since I usually keep them 20+ years.

That Odyssey emergency braking sounds scary. The Toyota safety system has worked perfectly for me (plus, who wants to change timing belts?).
 
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