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I have a 2nd generation 2005 Sienna, made in Indiana in January 2005. It's in great condition, so we thought, why not put a hitch on it and get a camper?

Every hitch I've shopped for shows that the connecting bolts as "M12 x 1.25 x 40mm," but after cleaning out the bolt holes on the frame, the M12 bolts are too large. When I tried some other bolts from my tool chest, I found that 7/16"-20 fine thread bolts fit perfectly!

I have a call into Toyota corporate for confirmation, but thought I would check here, too.

Anyone else found that their hitch bolt holes were 7/16"-20 instead of M12 x 1.25?
 

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I have a very hard time with the concept that Toyota drilled non-metric threaded holes on a 2005 Sienna. I have, however, read that the threaded holes for the hitch can get so incredibly corroded and mucked up over the years that it can be almost impossible to get them cleaned out enough to get bolts into them. My guess is that you still don't have the holes cleaned out enough for the correct metric bolts to fit.

You need to get this right unless you want to see your hitch and camper flying off your Sienna. I had some difficulty driving the correct six metric bolts into my 2014 Sienna and it was only a couple of months old when I installed the hitch.
 

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If you are in the rust belt, even a 3 year old van may need the treads chased with a tap. You'll find it near impossible to simply clean out the holes and drive a bolt in without this extra step. Lots of cutting oil and patience. Rotate a half turn, back a quarter and watch the rusty chips fall out. Remove the tap after a full turn and clean it and the hole well. If you don't do this slowly and carefully, you'll remove so much material that the bolts won't hold well and may strip out when tightened to the torque spec.

If in doubt, consider tapping one size larger and get larger bolts.
 

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after cleaning out the bolt holes on the frame
That is what makes this puzzling. How did you clean out the bolt holes? The advice offered here is good advice, especially carefully chasing the threads with a tap.

Your 7/16" bolt is 11mm. It is easy to imagine 1mm of crud left in there.

Let us know how this turns out and good luck,
bb

PS: I have a hitch for sale if you need one...
 

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Thanks so much for everyone's responses!

For the first cleaning, I used PB Penetrating Catalyst (http://blastercorp.com/PB-Blaster-Penetrant-remove-stuck-parts-spray), WD40, and multiple toothbrushes and rags to clean out the driver's side holes.

For further cleaning (not started yet), I got an Oatey 1/2 in. Heavy-Duty Fitting Brush (http://www.homedepot.com/p/Oatey-1-2-in-Heavy-Duty-Fitting-Brush-313272/100142649).

Some additional context:
* while the Sienna is almost 12 years old, it has less than 60,000 miles on it
* for most of the last 10 years, the Sienna has been driven about once a week and otherwise is in a dry garage in Ohio
* the Sienna has spent very little time in snowy weather, except for a few road trips

Once I use the new, stiffer brush I will post some before and after photos.
 

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The high surface area of drilled & threaded holes makes them a prime spot for rust. As you've got the brush already, give it a try. But unless it's pretty minor, I have my doubts that you'll get it done with a brush alone. I'm telling you from experience - spend the $10 and buy a tap! It was a size that wasn't included in my Sears Metric set, so picked it up at an auto parts store.
 
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I agree that using a tap is the best and maybe the only way to get these threaded holes cleaned out.

As much as I like supporting local stores, I can't imagine the auto parts and hardware stores near me in this 2 million plus population metro area having one in stock other than perhaps in a fairly expensive set. I gave up years ago chasing down Snap-On Tools trucks only to find that they usually had to order what I needed. I hit several local hardware and auto parts stores a few weeks ago looking for a 6-point 21mm 1/2 drive deep socket to use on Toyota lug nets and didn't find any at all. (I've rounded off too many lug nuts with 12-point sockets over the decades.) I gave up, ordered it online and got it in two days.

Amazon.com has a bizarrely large selection of M12 thread taps - many with "free" 2-day Amazon Prime shipping that would get it to you on Monday if you order today. It's disappointing to see the negative impact on local retailers and retail employment and seeing formerly thriving but now vacant shopping malls torn down, but I can't ignore the convenient of ordering products on a smart phone app and having them turn up on my doorstep or in my mailbox in two days.
 

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Hi, just wondering what the final outcome was for you; I cleaned my threads, could not get the bolts in, then ended up taking it to a shop nearby where I received confirmation that they didn't fit. I would like to believe it's possible that I need a smaller bolt, approx 11mm, but am v curious about your results! I know it's been a while at this point but didn't want to re-ask the same question. Thanks! Clive (2005 Sienna XLE)
 

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Hi, just wondering what the final outcome was for you; I cleaned my threads, could not get the bolts in, then ended up taking it to a shop nearby where I received confirmation that they didn't fit. I would like to believe it's possible that I need a smaller bolt, approx 11mm, but am v curious about your results! I know it's been a while at this point but didn't want to re-ask the same question. Thanks! Clive (2005 Sienna XLE)

The following is a quote from "Ask the Experts" at https://www.etrailer.com/Trailer-Hitch/Toyota/Sienna/2005/C13105.html?vehicleid=2005306404#exp-productdetails=.questions where I've bought numerous hitches, towing supplies, and bike racks: "The Curt Class III # C13105 trailer hitch attaches to a 2005 Toyota Sienna using M12-1/25 x 40 bolts."


If you need more confirmation, I suggest you call tech support at etrailer and ask even if you didn't buy your hitch from them - they've got great tech support people and should help you regardless.

Per previous posts in this thread, it is likely that you need to buy an appropriate tap and and use it and plenty of penetrating oil to clean the bolt hole threads.
 

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Those 2 thread pitches are the same so a 7/16-20 will thread in, should have some slop though.
But it will not have the holding strength a M-12 will.
I would run a tap thru it,
 

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Can someone share a link for the tap that would work for this? I'm currently dealing with this issue and want to make sure I get it right the first time.
 

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M12 x 1.25 thread pitch, IIRC.

I bought mine for around this price at a local autoparts store, but this should do it.

 

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I'm not sure if this is a new thing or not, but my 2018 sienna had the mounting holes covered with an adhesive vackednpiece of rubber. Not overly robust, so I'm not sure how long it would have held up, but the threads were perfectly intact when I got to them.

I know this doesn't do a thing to help the OP, but I figured it was at least interesting
 

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Thanks so much for everyone's responses!


Once I use the new, stiffer brush I will post some before and after photos.

Hey bud....you never came back OR posted pictures. I'm dealing with a 2000 that has spent only one winter outside of the desert, and has no rust. The threads look pretty clean, but I ran a wire brush through anyway. Well I tried; based on everything I read I was expecting 12mm holes so I bought a 1/2" pipe brush that I have virtually destroyed and still can't get it all the way through. There is no freeking way these are 12mm holes. I measure them at about 8mm with a caliper, and while they might not be totally clean yet there's no way there's 4mm of rust either. Would sure be nice to know what they are supposed to be before I go trying to tap them.
 

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You are dealing with a Gen-I, year 2000 van, so all bets are off on what hole/tread size to expect. Whatever Brightshade found probably won't apply....

Go to etrailer or other sellers site and see what they have to say. Pick a kit applicable to your model and download the instruction sheet and see what hardware is packed with it.

BTW, if the only hitch recommended by Toyota in 2000 was a Class I or II, it is possible that you could have 10 mm holes rather than 12 mm. I had that experience with Honda on a CR-V. But there is no way that even high grade 8 mm bolts would have the recommended shear strength for this job. I could believe it if you found 10 mm was correct on a dinky hitch.
 

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BTW, if the only hitch recommended by Toyota in 2000 was a Class I or II, it is possible that you could have 10 mm holes rather than 12 mm. I had that experience with Honda on a CR-V. But there is no way that even high grade 8 mm bolts would have the recommended shear strength for this job. I could believe it if you found 10 mm was correct on a dinky hitch.
You are correct as usual. An etrailer install video for a 2000 Sienna says the bolts are 10mm. Here is a link: 2000 Toyota Sienna Trailer Hitch - Curt
 

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Thanks, I knew I wasn't crazy. I can only measure the inner diameter of the threads from below so what looked like 8 mm could certainly be 10mm. I agree, I wouldn't want a hitch with 8mm bolts! This is a class III, 2" junkyard hitch I'm installing.
 

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Your limits are based on those 10 mm bolts and the frame they attach to. No matter what the rating of the hitch, consider your upper tow limit to be 2,000 lbs and a vertical load of 200 lbs. Maybe even less if the drivetrain has limitations.
 

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For future reference the specs for Gen 1 from the Curt 13511 datasheet are

QTY DESCRIPTION

(4) M10 - 1.25 x 30 HEX BOLT
(4) 3/8" WASHER
(4) 7/16 LOCK WASHER HELICAL LOCK WASHER
 
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