Fluid changes are cheap compared to rebuilt transmissions.

 

Nothing wrong with changing fluids early.
Your vehicle. Your money. Your call.

 

Yes, I do change my fluid on a schedule.My comment is only questioning why all like-transmissions maintenance schedules appear to be the same, regardless of the large weight differences of the vehicles they are installed in. The final drive ratios can be different, this may be a factor.

 

The Car Care Nut Channel guy, Ahmed, has done videos and has discussed when it's too late to do a change of fluid. It's an absolute that you don't flush it, it's strictly a drain and fill, but at 110,000 miles, it may be past a good, safe threshold. I would imagine that the gentler it has been driven, the safer it probably is to do a drain and fill. Not knowing exact capacities on yours, when I've done that job on two Toyota automatic transmissions about 25% - 30% of the fluid passively drained. I also let it drain a lot longer on both jobs. So I may have gotten substantially more by letting it drip for hours.

I've done a fluid change at 64,000 miles on a U760E 6-speed RAV4 transmission, I sent some fluid in for testing and they said it had less than 10% life left. That particular car was 90% freeway although it would regularly hit California traffic. One of the used RAV4s we bought had an ATFWS drain and fill at 98,467 at a dealership. Everything is great with that transmission now that it's at 122.5k.

Since the Sienna shouldn't be driven like a race car, that extra weight on that transmission shouldn't be too much of a stretch. Regular hard acceleration though may change that...

 

With that fantastic engine, it's hard to stay off the pedal, though!

 

With my '05, I used to drive from Las Vegas to San Diego every 3-day weekend... Occasionally, because the ride was so comfortable, I would look down and see me doing 85-90 miles an hour.

I remember a review calling it a Lexus minivan. Great and quiet. Nothing like my cramped and creaky 2025.