Can a 2005 Sienna be changed from 7 to 8 passenger seating?

My guess is that there is either a weight limitation or interference between the seat mounting system/seatbelt anchors and the drivetrain for the rear wheels.

I would not attempt a home made mounting system. Seats must remain anchored to the floor during a crash, and there is no simple way to be sure that a home made system will conform. Also, the seat belt anchors are different for bench seats than for the captains chairs so seat belts probably wouldn't work. Lastly, that middle bench seat may not be available as an assembly and if you buy it part-by-part, it is probably close to $1,000.

If you routinely carry 8 people, you may wish to check out the Sequoia - the third row seating is actually pretty comfortable.

One other thing to be aware of on the AWD Sienna is that it does not have a spare tire unless the previous owner opted for the spare tire carrier. Instead of a spare tire, the standard tires are "run flat" which allows the driver to drive a limited distance until the tire can be repaired.

How would you get passengers into the rearmost seat?

What Ray said.

If the standard model can have the 8 seat option, but the AWD can not, then there are structural considerations that must be thought about. The Sequoia sounds like maybe you should give it a look.

I was thinking of something like a steel plate that would bolt into the existing 7-passenger floor and contain a 'replica' of the 8-passenger bolt/track pattern on top. So the seats would end up elevated a bit. I think something like this would be as strong as the orginal design. But the drivetrain might be an issue if it creats a hump in the floor. And you have a good point about the seatbelts, that's not something I'd be comfortable 'adapting'.

Thanks for your thoughts, very helpful.

The Sienna is sold in both 7 and 8 passenger configs, so the mod I'm contemplating shouldn't limit access (I'd have to replace the entire

As I mentioned before, there is no easy way to test the crashworthiness of the modification and if it were my vehicle, I would not feel very comfortable doing this modification.

You're welcome!

If you try this and get involved in an accident while carrying people not in your immediate family, expect to spend a lot of time n court fighting lawuists. In fact, I guess you can't discount the possibility of lawsuits from your immediate family members, either.

It's kind of a moot point now because the sea tbelt issue has nixed the whole idea. But just to be argumentative, the fact that Toyota doesn't offer 8-passenger seating with AWD doesn't *necessarily* mean there's a structural issue. Japanese car companies limiting configuration options for business reasons. Perhaps Toyota thought there wasn't sufficient demand for this configuration to warrant manufacturing and importing it.

As far as the law suit th> What Ray said.

IMO, the most likely reason that the AWD versiosn is only offered in a 7 passenger configuration is weight. Among the factors when calculating EPA fuel economy is weight, and it is possible that the 8 passenger configuratio puts the vehicle into a different weight category. Weight is the reason why certain options like sunroofs used to have limited availability, and why even some upscale vehicles have space saver spares.

Aftermarket wheels and tires must meet the same safety standards that OEM wheels and tires do, and as long as the offset, tire circumference, bolt pattern, etc. are the same as stock, they are not inherently less safe than OEM wheels and tires.