I have a 2011 Toyota Sienna minivan with just over 200,000 miles on it. Recently it has developed a vibration issue. This typically occurs around the 45 mph mark give or take a few mph. The vibrations are occurring primarily when accelerating though there seems to be a little that continues as speed is maintained. There is no issue when decelerating. The shake seems to be coming more from the floor of the vehicle as opposed to simply the steering wheel. The tires only have about 10-15k miles on them. I recently had them rotated and balanced at the tire shop where they said they didn't think the issue stemmed from the tires.

What else should I be looking at as potential problems?

Does this happen at light throttle between gears or without downshifting?

Try putting in manual gear and running up to same speed.

Might be torque converter. Could also be engine or transmission mounts.

Suspension parts, struts, bushings, etc. If you're still on the original parts something has likely worn out.

I had two 2011's at one point. Now have one with 160K.

Had something similar and had to change out the motor mounts. Just recently had the control arms, shocks/struts, ball joints replaced.

I don't think I'll get well past 200k miles without something major needing replacement.

fixer said:

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Might be torque converter. Could also be engine or transmission mounts.

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TC was my first guess.

Thanks for the feedback everyone, I do sincerely appreciate your help.

I normally look at U-Joints in this scenario but the Sienna is FWD so that's not your issue.

My wife's 2011 Sienna is starting to need CV joints. For her it's a light slow speed clunk when turning that's more felt than heard. But that slop in the drivetrain might also be what you're experiencing as a vibration under load.

Any lights/codes?

A failing coil may exhibit some of the same.

Transmission fluid change history?

There's no light code showing. We had it the shop about 6 months ago to address the CV joint because we had that low growl sound. Got that fixed and thought the transmission fluid was flushed at that time, but I will have to check.

A couple of things.

One, never flush. Did they recommend a transmission flush at the time? When you remove the CV half shaft, there's always a little loss of fluid, but it just needs to top off.

Two. Did they use the correct fluid? This vehicle should use Toyota WS also known as world standard fluid. It cannot use a universal fluid, or even a fluid that says it's compatible. This is very sensitive. I believe the other choices are fluids made by Eneos or Aisin, which is the OEM supplier anyway.