Front axle arm bolts/nuts (1 Viewer)

[AZ80]

Would it be ok to swap with grade 8 hardware with a lock washer?
The oem bolts and nuts keep coming loose.
Teeth on the nut look suspect

-92 fj80

 

[Malleus]

The OEM hardware isn't Gr. 8; why was this installed?

To answer your question directly, there's no such thing as a graded washer. There are hardened washers, but the fastener grade is based on a tensile strength specification for the material. The extra torque required to meet intended the torque specification would need to increase, to account for the spring rate on the lock washer. There is no way to calculate this, the torque specifications start with a generic bending calculation of three thread forms, and then those values are validated by statistical testing.

You could, if you really wanted to be correct, put a spring (lock) washer under a press load, with a load cell, and determine how much force it would take to flatten it. That force would need to be added to the calculated force to bend three thread forms. The ratio between this value and the calculated force to bend just the three thread forms would, theoretically, give you the additional torque needed, in excess of the original OEM specification.

Even though I know all this, I wouldn't do it. I'd try to determine why the bolts were loosening and fix that. Toyota engineers are pretty good at designing these trucks so they don't fail.

 

[OGBeno]

Why not just purchase the correct replacement service parts from Toyota?

 

[OGBeno]

The OEM hardware isn't Gr. 8; why was this installed?

To answer your question directly, there's no such thing as a graded washer. There are hardened washers, but the fastener grade is based on a tensile strength specification for the material. The extra torque required to meet intended the torque specification would need to increase, to account for the spring rate on the lock washer. There is no way to calculate this, the torque specifications start with a generic bending calculation of three thread forms, and then those values are validated by statistical testing.

You could, if you really wanted to be correct, put a spring (lock) washer under a press load, with a load cell, and determine how much force it would take to flatten it. That force would need to be added to the calculated force to bend three thread forms. The ratio between this value and the calculated force to bend just the three thread forms would, theoretically, give you the additional torque needed, in excess of the original OEM specification.

Even though I know all this, I wouldn't do it. I'd try to determine why the bolts were loosening and fix that. Toyota engineers are pretty good at designing these trucks so they don't fail.

When material sciences get involved…

 

[AZ80]

Meant swap to grade 8 bolt/ nut and a lock washer. Lowes is across the street.

 

[jonheld]

Considering that this hardware keeps the axles located under the truck and Toyota specifies them as single use, I would purchase new OEM hardware and be certain about your torque settings.

 

[AZ80]

I

 

[Squeegee]

Make sure you’re torquing it to spec. I’ve always re-used suspension bolts and never had them come loose. If you’re still having issues just dab on a little blue loctite. Or just get a new bolt. And the oem bolts are metric, they’re probably a grade 12.9 or 10.9, not grade 8.

 

[gummycarbs]

I'm using grade 8 hardware because I need something longer to accommodate my caster plates ("washer mod", but bigger). Working great several years after the fact. Off the top of my head, I want to say that it's something like .5mm difference in diameter compared to the factory bolts. I'm pretty sure that I used fine-threaded fasteners.

Regarding lock washers, NASA says they're useless. I used plain washers.

Either way, it's *really* weird that yours are coming loose.

 

[UsedLuxury]

Make sure you’re torquing it to spec. I’ve always re-used suspension bolts and never had them come loose. If you’re still having issues just dab on a little blue loctite. Or just get a new bolt. And the oem bolts are metric, they’re probably a grade 12.9 or 10.9, not grade 8.

Use green retaining loctite. You'll never have that bolt come loose again.

 

[gummycarbs]

And the oem bolts are metric, they’re probably a grade 12.9 or 10.9, not grade 8.

(Just posting for clarity, because I wanted to double-check and it might help others. SAE Grade 8 is equivalent to Metric 10.9)

 

[AZ80]

Awesome appreciate everyone's input.

 

[Railwelder93]

The OEM hardware isn't Gr. 8; why was this installed?

To answer your question directly, there's no such thing as a graded washer. There are hardened washers, but the fastener grade is based on a tensile strength specification for the material. The extra torque required to meet intended the torque specification would need to increase, to account for the spring rate on the lock washer. There is no way to calculate this, the torque specifications start with a generic bending calculation of three thread forms, and then those values are validated by statistical testing.

You could, if you really wanted to be correct, put a spring (lock) washer under a press load, with a load cell, and determine how much force it would take to flatten it. That force would need to be added to the calculated force to bend three thread forms. The ratio between this value and the calculated force to bend just the three thread forms would, theoretically, give you the additional torque needed, in excess of the original OEM specification.

Even though I know all this, I wouldn't do it. I'd try to determine why the bolts were loosening and fix that. Toyota engineers are pretty good at designing these trucks so they don't fail.

That’s a funny way to spell, “get a new bolt”.

 

[Rusty Marlin]

The OEM hardware isn't Gr. 8; why was this installed?

To answer your question directly, there's no such thing as a graded washer. There are hardened washers, but the fastener grade is based on a tensile strength specification for the material. The extra torque required to meet intended the torque specification would need to increase, to account for the spring rate on the lock washer. There is no way to calculate this, the torque specifications start with a generic bending calculation of three thread forms, and then those values are validated by statistical testing.

You could, if you really wanted to be correct, put a spring (lock) washer under a press load, with a load cell, and determine how much force it would take to flatten it. That force would need to be added to the calculated force to bend three thread forms. The ratio between this value and the calculated force to bend just the three thread forms would, theoretically, give you the additional torque needed, in excess of the original OEM specification.

Even though I know all this, I wouldn't do it. I'd try to determine why the bolts were loosening and fix that. Toyota engineers are pretty good at designing these trucks so they don't fail.

To simplify this... torque the bolt to 85% of yield strength and call it a day, but don't forget to account for lubed or dry. The lock washer has nothing to do with torque as the load to flatten it is a single digit percentage of the load to put the fastener into proper tension. Your torque wrench will have greater error than accounting for the lock washer.
The rest has been covered, like there's no such thing as grade 8 metric hardware, and NASA's stance on lock washers being a waste of money, and trust me on this, don't use green loc-tite on anything you might ever someday want to take apart, that s***'s forever!
Oh and here's the torque calculator,

Bolt Torque Calculator

Calculate required bolt torque.

www.engineeringtoolbox.com

And all of that crap above aside, just buy the right hardware. Torque to spec and sleep easy at night.

 

[BILT4ME]

Make sure that you're only turning and torqueing the PART WITH THE WASHER ON IT! The Toyota nuts have four "tabs" on them to bite into the plate steel of the frame so they don't come loose.

To remove the bolts, you must only loosen the part that has the washer. The part in direct contact must NOT be turned or it will gouge out the part of the frame that provides the "grip". Once that area is wallowed out, no replacement part will hold and stay tight because there is nothing left to grip on. You may actually need to weld in the circle of area that has been gouged out and grind it smooth.

Then install new bolts and nuts from Toyota.

Use a torque wrench. Follow the FSM.