99 Toyota Sienna - Aisin A540 Transmission Issues

[kschachn]

The transmission on my Sienna is starting to act up. It has been doing weird things for the past 25,000 miles or so, but lately it is getting worse. It still shifts OK and there is no flare between shifts, but it is acting "harsh" or shudering, especially on a downshift. I don't know how else to describe it, at first I thought there was a broken engine or transmission mount but I replaced them and that didn't cure the issue. I'm pretty convinced now that it is the transmission itself. Another description is that the harshness is kind of "bouncy", just like if one of the mounts was broken. When you are driving along at a steady speed everything is fine, you really notice it only when accelerating or kicking down to pass someone at a relatively slow speed.

Obviously with over 320,000 miles it has seen its tour of duty, but any suggestions as to what might be wrong? I have kept up with regular fluid changes (M1 ATF) and this last time I added Lubegard which had no affect. When clutches in an A/T wear out what are the symptoms?

We still use the van for daily driving, and the engine is good so I am entertaining the idea of a repair or replacement. Suggestions on that are welcome too. A Toyota "OEM" rebuild is about $2000. I've rebuilt everything on a car except an A/T, parts are readily available but I really don't want to go through all the work just to find out it doesn't operate properly, besides the fact that I don't have the 1,00,000 special tools the manual seems to indicate I would need.

 

[zzyzzx]

When was the last time you changed the transmission fluid or filter?
Are the axles the original (I am assuming this is front wheel drive).

 

[kschachn]

Originally Posted By: zzyzzx
When was the last time you changed the transmission fluid or filter?
Are the axles the original (I am assuming this is front wheel drive).


About 10,000 miles ago, and no the axles are not original. When I put in new engine mounts I replaced the axles since the R/H one runs through the rear mount (and it is usually a destructive removal). Deterioration of the rear mount was Internet lore for the symptoms I was experiencing, but it turned out to be incorrect. The new axles are Toyota remans from the dealer.

 

[440Magnum]

My best guess:

If you hooked it up to a transmission scan tool, you'd probably find that all (or many) of the adaptable parameters are maxed out due to clutch wear. Banging into gear, especially on downshifts, is a pretty classic symptom of the transmission using all the clutch apply force it can to compensate for clutch actuator volumes that are at or beyond the limit. It may run that way for quite a while (or another 15 minutes...) but eventually a clutch is going to start slipping and then it will fail VERY quickly from overheating.

Transmission rebuilding is easier than a lot of people think and you can concoct substitutes for many of those specialized tools. But I'd learn on something like a 1970 Turbo 350, not on a modern transverse electronic transaxle going in my daily driver. On a lot of those, there's a learned feel for where within the tolerances everything should be set up for a build that will last. The temptation is to always get things at the "tight" end of the range to allow for wear, but that sometimes just leads to early failure on that kind of transmission.

 

[zzyzzx]

I also think you should check for codes.

 

[Rand]

probably need some kind of specific toyota only scan tool to see anything interesting.

 

[CourierDriver]

16 years old, well it might just need some attention...

 

[JC1]

Sounds like you are thorough on the Tranny fluid changes. I'm assuming you cleaned the pan when you changed the filter/strainer?

I'm wondering if changing the shift soleniods would make a difference? They can be an issue in some of the Toyota Tranny's.

 

[kschachn]

Originally Posted By: JC1
Sounds like you are thorough on the Tranny fluid changes. I'm assuming you cleaned the pan when you changed the filter/strainer?

I'm wondering if changing the shift solenoids would make a difference? They can be an issue in some of the Toyota Tranny's.


Yeah I cleaned the pan for about half of the changes, I actually posted some pics here from time to time. There wasn't a lot to see so for the other half of the changes I just did a cooler line exchange or sometimes just a drain and fill.

And idk about the solenoids, I might look into that a little. At this point I'm just going with 440Magnum's comments and assuming the thing is just plain worn out.

 

[JC1]

Have you ever thought about using a different tranny fluid? I've been using max life its half the price of mobil 1 and I didn't notice a performance difference in my 98 Sienna.