What year is your Sienna? If it's not a sealed transmission, you are ok to leave a little bit more fluid in the system. It won't hurt anything.Hi. I'm new here, but have the same question about ATF level.
I bought used van in December 2013. Previous owner did nothing about transmission, so I first did drain & refill, then did drain & refill with dropping pan. It was WOW... How dirty it was.
I put the same amount of ATF that I drained, but I read ATF level higher than top notch on the dip stick with engine running.
Is that okay, or should I do another drain & refill to adjust ATF level to between two notches?