This guy is onto what happened. Someone over-torqued them - a lot. You can see thread-stretch there. That's why it broke.

Normally, they can be re-used with no issue. And, the extra torque does nothing at all when there's splines to keep them from twisting in the first place. Someone hit them hard with an impact gun...

 

TTY or not the "book" says to replace them, but it says to replace nearly every bolt & nut that has a hex head.

TTY means that the bolt actually stretches to make a repeatable precise clamping force. They are verrry expensive because they are specially formulated metal.
Not all torque plus degree bolts are TTY.
All TTY bolts are torque plus degree.
The only mention of TTY in the shop manual is a definition.

There is another type of fastener called Prevailing Torque that is designed to deform when tightened to lock the threads. Like squash nuts or nylon interface nuts and bolts with preapplied adhesive. They have a "minimum torque developement" spec.

I think the names get scrambled a lot.

 

Lower strut bolts from the manual:
So while they are not TTY, the prevailing torque might put extra stress on them.

 

In this case the prevailing torque part is the splines and theoretically should be replaced since they are designed to deform.

 

here’s the definition of TTY bolts

https://en.wikipedia.org/wiki/Torque-to-yield_fastener

mine was askew

 

For now, I replaced the two broken/deformed ones with M12-1.75 class 8.8 bolts from Home Depot and torqued to 70 ft/lbs with class 8.8 tension lock nuts. That is the highest torqued I can use on these type of nuts and bolts, so it will be like this until I get new ones. Tension lock nuts should compensate for the other 19 ft/lbs.

 

That ought to hold the knuckle in place firmly

 

Look let's get real.
I have torqued down many 3406 Cat engine heads using the same bolts over (330 lb ft). If the shank,or shoulder, of the bolt looked bad replaced it. Why? Google it.
Con Rod bolts on a 3500 engine were mandatory to replace ever time you did a lower end rebuild. That's an engine that has 263 cu in per cylinder. Which I have built many times.
I have torqued down TTY head bolts when those style "came out" and after knowing what the value was just tightened them down to a known torque value. Didn't do step #1 then step #2.
Every bolt has memory. A bolt is a spring.
Yes tightening a bolt does hold something together, but it's the clamping force applied do to the stretch spring effect.
You gorilla a fastener and it will break.

 

Can anyone give me a part number for these? I broke one as well...with a small ratchet. Didn't even get to the torque wrench yet. All local auto part stores can't find them.
THX!

 

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