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I just bought a 2007 Sienna with 47k miles on it and appears in great shape. Have a 3 mo powertrain warranty. I've had two Hondas but first Toyota and I'm questioning if there is a transmission problem or if it's just different than the Honda.

Symptom: When I'm traveling at low speed (5-10 mph), presumably in the lowest gear in parking lot for example, and take my foot off the gas momentarily, when I start again to accelerate, the engine revs up slightly and then appears to shift into gear again. It's relatively subtle but noticeable. No other issues or problems and appears to shift smoothly at all times.

I'm trying to find out if this is normal for this AT or a symptom of a developing problem so I can utilize the 3 mos warranty before it expires in 45 days. Thanks in advance for any help. Please don't worry about telling me it sounds normal and me being upset if I run into a problem down the road. The issue is so subtle that I would not be surprised if it's just a unique quirk of this AT and if it is, I could certainly have an unrelated problem develop.
 

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My suggestion would be to take it in and have them note what you are bringing it in to have them check out. If they say there is no problem and you end up having a problem down the road, you have some documentation that it started under the warranty period.
 
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Sounds normal to me. In my experience, many automatic transmissions have some similar effects at low speeds and really low throttle positions. Maybe try changing your transmission fluid with a few drain and refills or using the transmission cooler lines to see if that improves it.
 

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My two recommendations for your van would be to make sure the vvti oil line recall has been done. Also if your van has the tow prep package, replace the rubber line to the steel version!
 

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I agree with the recommendation to change the fluid. ATF-WS is supposed to be a long-life ATF, but it is also somewhat hygroscopic, meaning it absorbs moisture from the air. 47k miles is low, but on a 14 year old vehicle it could still be time for a fluid & filter service.

The going opinion here seems to be that these transmissions are fairly sensitive to ATF cleanliness, and Toyota's 100,000+ mile ATF change intervals aren't necessarily ideal for a Sienna owner who wants to go for reliable high mileage.

Neither of our Siennas has done quite what you describe, but our '06 dropped out of gear for 20-30 seconds in heavy traffic on the highway right after we got it, and our '08 had a quite prominent 3->4 shift synchronization issue when we got it. We've accelerated fluid changes/exchanges, and in 2½ years the '06 has never glitched again, and the 3->4 glitch on the '08 is rarely noticeable anymore as well. But on our '08, it took some time for the shifting issue to gradually go away (it was most likely caused by a solenoid problem, and there isn't good fluid flow in part of the solenoid to quickly clean it out).

We've also used some Lubegard Red, but I don't know for sure how much it has helped (in comparison with simply ensuring the fluid is nice and clean). We also have installed Magnefine in-line filters and additional ATF coolers on our vans.

The 5-speed is one of the better transmissions Toyota has used (the 4-spd, 6-spd, and 8-spd have apparently all had more issues), but it is sensitive to fluid cleanliness.

- G
 

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09 FWD here. I have noticed that as well. I wouldn't be worried at all. Welcome to the Sienna family!

That is a crazy low mileage for an 07. Congratulations on the find. I hope it serves you well for many years to come! We are happy owners of an 09 purchased last summer with 120k on the clock.

I would definitely recommend taking a look at the VVT-i and oil cooler lines. I wrote up a post about the VVT-i oil line here: Summary of VVT-i oil line failure The oil cooler line is a similar problem; you can search around for info on that.

I would also recommend doing a few transmission drain and fills due to the age. If you don't want to spend the money for OEM ATF-WS, many here (including myself) think Valvoline MaxLife is a great option as well.
 

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As I was thinking about this tonight, I'm wondering if this phenomenon is just the transmission having downshifted back to 1st gear in premature anticipation of a stop - it feels like the engine is revving in neutral but the trans is in 1st where 2nd would be more appropriate.

If that's the case, this is just a shift logic nuance that isn't a concern at all as far as reliability.

- G
 

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My '06 started doing that around 55k miles. I pulled the dipstick and the fluid was still reddish colored but started to shift a little towards the pink/brown stage. I did a drain and fill (at 60k) and the hesitation/slippage was gone. I have the fluid and crush washer at the ready to do it again when the weather warms up in the Spring, as the van is just starting to do the same type of thing again.
 

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My 06 has been doing that since I got it about 3 years ago with about 100k. I did 2 drain & fills so far. The fluid was almost black before the first D&F. It now has about 150k and I am going to do another one soon.
*Another thing that I am now concerned about. The trans downshifted in traffic (3rd to 2nd?) the other day with a loud bang like a hammer hitting metal. The only time it has happened so far. Anyone have a similar experience or know what it might be?
Should I be looking for another vehicle?
 

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dscott,

My 06 has 230K on the original transmission and it's done that same thing since I purchased it with 100K on it. I change out a gallon of transmission fluid on every third oil change and I changed the filter at 200K (didn't need to, it was clean as a whistle). I started doing the transmission fluid changes right after purchasing it as I know most minivans are tough on transmissions. But the fluid/filter changes haven't changed that symptom. Makes me wonder if one of the valves is just not engineered properly or doesn't work like it did when new. Either way, I wouldn't worry about it, but I would do a couple flushes with the oil changes. I just use a long, skinny tube down the dipstick hole and siphon out as much as I can get. That normally gets about 1 gallon of fluid out each time. It's a slow process, but leave it siphon overnight.

Congratulations on your purchase and welcome to the site.

Tom
 

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Yeah I will add that my 2007 does this exact same thing. It's always in those abnormal/unexpected moments, like when you're coasting to a stop, but then the light suddenly changes and you start pressing the accelerator.

I just figure the transmission was in some other gear, or almost like it was in neutral, and suddenly had to get into the right gear in an unexpected situation. Normal acceleration from a stop is always smooth and solid.
 
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That's pretty normal. It was the most notable thing about the transmission when I first bought it. I now have 191k miles.
 

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I've just noticed this recently on a couple of occasions. Same scenario as the op posted. My Sienna acted the same exact way. Maybe it's been like that all along and I just never noticed it until now
 
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