[GeeTeeOhh]

So, in doing my due diligence on checking out a used differential for my GTO, I was checking the ring gear bolt torque, case bolt torque, etc. The case bolts seemed loose, so looked up the spec, 30 +- 1 ft-lbs torque, set the wrench and one of the bolts snapped off about 3/8" from the threaded end. Now, I am looking for a bolt. Any suggestions where to go for that?. More concerning is why this bolt snapped in the first place. It was wet with lube. the re-assembly instructions say to clean everything and lube the bolts with motor oil. I know torque values can change significantly with dry vs. lubed.

This is on a 1965 Safe-T-Track with 3.23 gearset. The bolt is 3" X 1/4" Gr. 8 with 1" of threads. Anything special about these bolts? I will check the local Fasteners inc today.

Thanks for any help

[mgarblik]

Those long fasteners are small diameter and a common breakage point for those cone style limited slip units. 50+ years of strain and stress on those fasteners and it's not at all unusual for them to fail. 30 ft. lbs. on a 1/4" fastener, even a grade 8 bolt is well into the elastic range of that bolt. Are you sure they aren't 5/16" fasteners? Either way, McMaster Carr would be a good source for replacements. Possibly MSC, or Grainger. In each case, try to verify the new fasteners are Grade 8 AMERICAN MADE. Grade 8 Chinese made bolts mean absolutely nothing! They will put grade 8 markings on any kind of bolt. In a critical fastening situation, I only use American, German, or possibly Japanese fasteners from a known manufacturer. NOT Chinese.

[GeeTeeOhh]

I think you are right on the 5/16" diameter, as the hex head size is 1/2". Time to get out the readers I guess...I will see what I can find at Napa or Fasteners, and look for American made....

And good point on the age - maybe I should replace all of them. I just hope I can dig out the remains of the end that broke off. Maybe this is a sign that I should replace the diff with a current design LSD haha. That will send me down yet another rabbit hole as I wouldn't know where to start.

[Formulas]

It could of very easily been over torqued from previous ownership

What is the exact length are they as they are close to pushrod cover bolts in appearance in a coffee can

Also you may want to closely inspect the rest of the carrier bolts for over torque they get skinny from stretching at the failure point

[Schurkey]

Originally Posted by GeeTeeOhh

looked up the spec, 30 +- 1 ft-lbs torque, set the wrench and one of the bolts snapped off about 3/8" from the threaded end.

When was the last time you sent off your torque wrench for testing/calibration?

I've used Angle Repair, and TeamTorque. Got good service from both.
https://anglerepair.com/

http://www.teamtorque.com/

Originally Posted by GeeTeeOhh

Now, I am looking for a bolt... ...The bolt is 3" X 1/4" Gr. 8 with 1" of threads.

I'm no expert. I can't picture a 3" X 1/4, or a 3" X 5/16 bolt anywhere in that assembly.

Got photos?

[GeeTeeOhh]

I don't have a picture of mine, but here is the same diff. They are the bolts that keep the case halves together, are just inside the ring gear bolt holes. I have indeed confirmed they are 3" X 5/16" with 7/8" threaded length. Luckily I found them at my local Fastenal. Going to replace all of them.

Good point on the torque wrench calibration. I am upgrading my torque wrenches and getting rid of some Harbor freight models. I will keep my NAPA 1/2 drive click wrench and may send it out for calibration.

[mgarblik]

You would think I would be telling everyone to throw out their Harbor Freight torque wrenches. But I can't honestly say that. We have a digital electronic torque tester (Snap-On) at my school. Students provide their own tools so we have them test ALL their torque wrenches the beginning of each semester. To my surprise, the Harbor Freight stuff is about middle of the pack, averaging +-5% which is typical of mid grade stuff. That's at 100 ft. lbs. You just never know how your wrench will test out. Split beam like the Snap-ON TQ series are the most consistent. Most brands of electronic ones are +- 2-3%.

[lust4speed]

FWIW my '67 service manual says 25 foot pounds.

[GeeTeeOhh]

Originally Posted by lust4speed

FWIW my '67 service manual says 25 foot pounds.

Thanks for the info...I may go with that, even though my 1966 service manual says 30 ft-lbs

[Schurkey]

Originally Posted by mgarblik

You would think I would be telling everyone to throw out their Harbor Freight torque wrenches. But I can't honestly say that. We have a digital electronic torque tester (Snap-On) at my school. Students provide their own tools so we have them test ALL their torque wrenches the beginning of each semester. To my surprise, the Harbor Freight stuff is about middle of the pack, averaging +-5% which is typical of mid grade stuff. That's at 100 ft. lbs. You just never know how your wrench will test out. Split beam like the Snap-ON TQ series are the most consistent. Most brands of electronic ones are +- 2-3%.

Your students are likely showing up with fairly new "Hazzard Fraught" torque wrenches.

One wonders how they test after five or ten years of accumulated wear from professional use.

I bought my Mac torque wrenches in the early-90s. Used professionally until '03, then hobby use since then. Sent them out for testing in 2017; they both passed, as did a Government Surplus inch-pound unit that has a manufacturing date of 1974.

[mgarblik]

Originally Posted by Schurkey

Your students are likely showing up with fairly new "Hazzard Fraught" torque wrenches.

One wonders how they test after five or ten years of accumulated wear from professional use.

I bought my Mac torque wrenches in the early-90s. Used professionally until '03, then hobby use since then. Sent them out for testing in 2017; they both passed, as did a Government Surplus inch-pound unit that has a manufacturing date of 1974.

That's very true. The micro-adjusting style, (extension spring) are very dependent on returning them to the relaxed position after every use. My father bought me a Craftsman 1/2 one for my 16th birthday in 1974. I treasured that torque wrench and took exceptional care of it. I tested it at the school a couple years ago and it was within 2-3% after all those years. I retired it as a memento of my dad, but it could still be used and relied upon.