Trailer Hitch Plate Weld on Nut Size

Anyone know the size of these weld on nuts located on the rear frame rails for mounting the reinforcement plates for the hitch? Thread size and pitch? I have a 2008 Tacoma.

 

I may be wrong but I don't believe that Toyota welded those nuts on there, that looks like a pretty sloppy weld for OEM. Now that being said, they do look similar (if I remember correctly) to the actual nuts that thread onto the bolts holding the hitch plate in place... I would start by calling your local Toyota dealer and getting a part number for that nut (if they are the same ones) and do a little digging around to find the thread pitch using that part number. You can always ask the dealer for a "hitch diagram" or "bumper diagram" that "shows all the hardware required for complete replacement."

 

These are what are there from the factory. I'm disassembling the rear end so I can get the frame rails in the back replaced due to an accident. I noticed these there after removing the hitch plates.

Anyone think I can get away without having these welding on to the frame? When I reinstall the hitch, can I just use locking washer on there? Is there enough hand room to get in there to hold the nuts in place when tightening? I'm guessing no as this is probably why they are welded.

 

Mine are

$13 M12x1.25 mm Self-Locking Nylon Insert Hex Lock Nuts, Pack of 6

M12x1.25

 

Toyota welds them on to make it easy on the assembly line for the assemblers. Toyota also pins the mounting brackets so there's no alignment issue. Just assemble it and go on to the next one. It makes for a very precise assembly with no guesswork for the assembly line. There should be enough room for tool access.
When I replaced my bumper with an aftermarket one, I couldn't use the OEM mounting angle brackets so it took a little finessing to get the bumper and box fit pleasing to the eye.

 

Bump

 

When I added my hitch, I ran a tap thread cleaning through the nut, and it was definitely 12mm x 1.25, same as TnShooter said above.

 

I answered him 2 post above your “bump?

 

Thanks, fellas! Anyone know what the part number for those nuts are so I can order new ones for the install? I was at the dealer today but the parts diagram did not show a part number. I'd like to get automotive strength nuts instead of something cheap at Lowe's or HD!

 

You aren’t going to find the weld on nuts.
They are part of the frame. I’ll have to see what the torque spec is for those bolts and match it to the grade nut/bolt.

I guess I could crawl back under mine and look a the head of the bolt and see what grade it is? But it’s raining now.

I will see what I can find.

 

Hitch installation.pdf - Bolts torque to 86 ft/lb.
https://images.thdstatic.com/catalog/pdfImages/98/988d3538-c02c-4e62-9793-70cbc436c4ff.pdf

However, the bolts look to be plated.
And I can’t find a chart that shows the marking our bolts have.
I’d go with grade nothing less than 8.8 and ideally 10.9. Just to be safe.


Here is the bolt hard stamp, maybe some one else can have better luck identifying the grade bolt?