Definitely drain and fill. Multiple times if you want. Too much risk with a flush.


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Avoid the potential risk of A/T flushing. Instead, do several A/T drain/refill cycles. Use a good import ATF such as Castrol Import.

 

Use a good import ATF such as Castrol Import.

 

Thanks! Since you both suggested multiple changes, how many miles apart should I change the trans fluid?

 

It probably doesn’t take long for it all to mix, but at any rate the first time I did mine I went 3x, 1k miles in between. Then once a year after that.


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Slowly moving the shifter through all gears several times with the engine running should be sufficient.

 

The 1998 Sienna owners manual recommends DEXRON 1, 2, or 3 automatic transmission fluid. Any recommendations?

 

Safest option is to just drain and refill the oil pan 3 times over a period of days or weeks with a conventional Dexron III fluid like the two pictured below. That way the transmission will gradually get cleaned up inside. Dexron VI fluids are extra thin and I'd worry they would cause accelerated wear in a transmission like the '98 Sienna's that was designed for the thicker viscosity of a Dexron III fluid.

 

 

TRANS EXPERT WANTED: 98 Sienna did NOT shift into gear this one time...

I bought a 98 Toyota Sienna with 115,000 miles on it three weeks ago. It runs beautifully and all gears shift perfectly - except for this...

The *Check Engine light went on 8 days ago so I stopped, turned the car off, and checked online to see what the problem could be. A website said to tighten the gas cap so I did. Another site said to press the odometer button and keep it depressed while I started the engine to reset the Check Engine light. I did that and the mileage on the odometer went away and when I pressed and released the odometer button it showed the number "1" where the mileage would normally be. I pressed and released it again and it showed the number "2" and each time I pressed and released it it would show the next number all the way up to the number "20" and then it would repeat starting at number "1" if I pressed it again, etc.

HERE'S THE PROBLEM:

While the engine was still running after doing the odometer button thing described above I put the Sienna in Reverse to leave and instead of going in Reverse it slowly rolled backward as if it was in Neutral (Car was on slight incline). Then I put it in Drive and again it didn't shift into gear but rolled slowly backward like before as if it was in Neutral. At that point I shut the engine OFF and started it again and it went into gear immediately and it's run perfectly ever since. Again, this not going into gear thing only happened that one time in the last three weeks I've owned it while I was doing the press the odometer button thing.

-The transmission fluid is at the proper level and appears fairly clean and not burned looking at all.
-I called the service department of the local Toyota dealership and he said there's no way that what I did with the odometer button could effect the transmission.

QUESTIONS:

1) Does anyone know why it wouldn't go into gear that one time in the three weeks since I have owned it?

2) Was there any connection to what I was doing with the odometer button?

3) Any suggestions for how I can find out conclusively if the tranny is going bad?

Thanks a lot!

*P.S. The Check Engine light code was for a faulty O2 sensor.

 

2) Was there any connection to what I was doing with the odometer button?

No. Just a coincidence.

 

I've been busy so I'm finally getting back to this thread. THANK YOU EVERYONE FOR YOUR INPUT AND THE DIAGRAMS, ETC. If any of you are transmission experts then it would be greatly appreciated if you could please go to this thread: http://www.toyotanation.com/forum/2...rans-expert-wanted-98-sienna-did-not-shift-into-gear-one-time.html#post13042226

Thanks

 

That link isn't working for me

 

The transmission does not appear to have a replaceable filter.

 

I have never heard of a transmission filter before but the guy in this video at 02:30 is changing the transmission filter on this 2002 Sienna.

1998 Toyota Sienna transmission filters for sale on eBay:
https://www.ebay.com/sch/i.html?_od...a+transmission+filter.TRS1&_nkw=1998+toyota+sienna+transmission+filter&_sacat=0

 

It looks like what is referred to as the "oil strainer" in the diagram I posted. Perhaps they are one and the same.

https://www.toyotapartsdeal.com/oem/toyota~strainer~assy~valve~body~oil~35330-32031.html

 

So do I need to replace that?