Can we tow with a '10 Sienna with no tow prep pkg installed?

My husband and I are in the market for a family vehicle that we can make our primary tow vehicle. We tow a lightweight camper (Livin Lite Quicksilver 10.0, weighing in at less than 2,000lbs fully loaded) with our Subaru Outback (towing capacity of 2000lbs), but have found that a minivan with a maximum towing capacity of 3500lbs would meet our needs. The minivan we have in mind, a 2010 Toyota Sienna, states that the towing capacity is standard/maximum 1500/3500. A footnote on the Toyota website indicates that a towing prep package (installed at the factory, I presume) would be necessary for towing. The van we have test driven (XLE AWD) did NOT have the towing prep package installed on the particular van. Does that mean we can't tow to the full 3500 capacity? What is the difference in standard/maximum towing capacity anyway?

Factory towing package vary a lot by manufacturer, model, year, mood of the engineers, it the groundhog saw on groundhog day, etc.

I will give you two examples.  On my previous vehicle, the tow package consisted of a Nissan factory hitch receiver and it was pre-wired, that's it.  I still had to get a pigtail to plug in the pre-wired module.  I also had to do the necessary wiring for the 7-pin connector and wire my brake controller from scratch.

On my current (GMC Sierra), the towing package consisted of a transmission cooler, trailer hitch receiver, pre-wired with 7-pin connector already setup in the rear, larger alternator, larger air filter and the brake controller was prewired, I just had to connect my brake controller to it.

While it is nice to have the factory tow package on most vehicle because you get things you do not get if you just buy a hitch, it does not mean you cannot equip your vehicle to tow properly.

So at a minimum, you need a trailer hitch (that's an obvious one).  The trailer wiring can be done by any trailer shop or yourself if you are good with that stuff.  I would certainly add an auxiliary transmission cooler, they are around 100$ installed, that is heck of a lot cheaper than a burnt transmission.

With a trailer around 2000lbs, I would personally would want electric brakes too, it will require a brake controller inside the van, plus brakes on the trailer axle if not already equipped.  While being able to tow the load along fine, I am more worried about stopping then driving.

Also, when they say 1500/3500 lbs, they usually mean 1500 lbs without a weight distribution hitch and up to 3500$ with a weight distribution hitch.  So with a weight of around 2000 lbs, you are over the 1500 lbs, so you will need a weight distribution hitch, which is never included with any towing package since it needs to be sized for the trailer you are towing.

So the list of things you need is:
trailer hitch receiver
weight distribution hitch
wiring for trailer
transmission cooler (optional but highly recommended)
trailer brakes (optional but highly recommended)

If you have all these, you should be in good shape.

I found a reference to the towing package in a 2007 Sienna brochure. A new one is likely the same:

I have the 2007 Sienna brochure, and here's what it says:

Tow Prep Package - 3500 lb towing capacity with heavy-duty radiator, heavy-duty fan, 150-amp alternator and power steering oil cooler.

Click to expand...

That would mean that you need more than just a weight distribution hitch to exceed 1500 lbs.  However, you probably don't need the big alternator to tow your little trailer and I would think the addition of an auxiliary transmission oil cooler and maybe an auxiliary fan could substitute for the heavy duty radiator since you will be at 2000 lbs tops.  Problem is, there is a risk that Toyota might not agree if you ever made a warranty claim on transmission, engine cooling, etc.  You might ask the Service Manager at a Toyota dealership about a towing upgrade to 2000 lbs for a Sienna and see what he offers (if anything). Doing it their way helps make you legit.

After comparing an itemization of what was in the 2010 tow package with what is standard on the Sienna XLE without the tow package, the only difference is the lack of an oil cooler on vans without the tow prep package.  Toyota can't/won't? add this after market, and they don't ship AWD XLE models to our region (lack of market?), so at this point we're looking at AWD vans with tow prep packages in the NE and they'll be going up to pick it up for us and driving it back down so we can get what we want.  Hope to find out by tomorrow if our negotiations will have us in our new TV by the end of the week!  If not, no loss.  We'll wait until the right deal comes along.  Our Subura does a great job of towing the trailer we have.