Sweptline.ORG

I have a 66 Powerwagon with a Dana 44 front diff. About 2 weeks ago, the six "grade 8 bolts" that hold the spindle,backing plate to the steering knuckle on the drivers side had failed right after I hit the brakes to make a stop. Has that ever happened to anyone out here????

Bet that woke u up!

Potential high shear load bolts should be grade 5. Less likely to snap. Grade 8 is harder, but more brittle.

There is no shear load on these bolts, as there is a shoulder on the spindle that fits tightly into the knuckle bore.

digdoug wrote: ↑

Mon Sep 30, 2019 5:24 pm

There is no shear load on these bolts, as there is a shoulder on the spindle that fits tightly into the knuckle bore.

I would assume that a brake would transmit angular shear through the bolts into the knuckle.

Wildergarten wrote: ↑

Mon Sep 30, 2019 11:44 pm

digdoug wrote: ↑

Mon Sep 30, 2019 5:24 pm

There is no shear load on these bolts, as there is a shoulder on the spindle that fits tightly into the knuckle bore.

I would assume that a brake would transmit angular shear through the bolts into the knuckle.

Ok,shear,I'll go with that.

How do you know they were grade 8? Is this a known fail? Seems like a lot from just hard braking.

They had the markings of a factory grade 8 bolts

WD wrote: ↑

Mon Sep 30, 2019 5:55 am

Potential high shear load bolts should be grade 5. Less likely to snap. Grade 8 is harder, but more brittle.

Please explain why the flywheel and flex plate bolts, which are under nothing but massive shear forces, are grade 8?

Every big rig and farm tractor shop/mechanic I’ve ever dealt with. Every chassis building article/video, print-online-dvd.

High clamping load? 8
High shear load? 5

Are they right? Are they wrong?

The 230 I gave the column shift 3spd, bellhousing and clutch away from used all Grade 5. My 318/727 and 413/727 have grade 5 for the torque converter and crank flange. Grade 8 spindle bolts. Grade 5 motor mount bolts. Grade 8 bumper mount bolts.

D100 and M400 chassis.

Rev the engine, sidestep the clutch and lay rubber for miles - the shear on those flywheel bolts is out of this world! In comparison, shear on the knuckle bolt is jack *#%^!

PwrWgnDrvr wrote: ↑

Wed Oct 02, 2019 9:40 am

Rev the engine, sidestep the clutch and lay rubber for miles - the shear on those flywheel bolts is out of this world! In comparison, shear on the knuckle bolt is jack *#%^!

Thanks for shearing.


John

WD wrote: ↑

Wed Oct 02, 2019 5:32 am

Every big rig and farm tractor shop/mechanic I’ve ever dealt with. Every chassis building article/video, print-online-dvd.

High clamping load? 8
High shear load? 5

Are they right? Are they wrong?

The 230 I gave the column shift 3spd, bellhousing and clutch away from used all Grade 5. My 318/727 and 413/727 have grade 5 for the torque converter and crank flange. Grade 8 spindle bolts. Grade 5 motor mount bolts. Grade 8 bumper mount bolts.

According to the science here, they're wrong:
http://rtstools.com/are-grade-8-bolts-m ... -9-metric/
One common misconception about bolts is that a higher rated bolt is stronger, yet more brittle, and therefore lower grades should be used in places like in suspension systems so they can deform rather then break. This is wrong!

Its often in the shear aspect that people assume lower grade bolts are better in places like suspension systems.
However, as you can see in the following table, both tension and shear are higher in Grade 8 bolts over Grade 5 bolts; in fact over 21% higher in shear and 25% in tension.

To be fair, the higher the grade of bolt, the harder it becomes as rated by the rockwell scale.
Therefore, technically a Grade 5 bolt is softer, and therefore spends more time deforming before failure. This time and area of deformation is called the plastic range.

However, as you can see by this graph, even though the Grade 8 bolt spends much less time in its plastic range, it doesn’t even get into the plastic range until it experiences over 21% more force. This same 21% of force, would have elongated and sheared the Grade 5 bolt.

So to use a lower grade bolt for the the purposes of it bending versus breaking, unfortunately that is incorrect. The lower grade bolt will reach its maximum elongation and reach its fracture point well before the higher grade even begins deforming.

I have a feeling that they were not torqued right last time someone had the knuckle apart. i have seen that happen on many old jeeps but never on any dodge 4x4

Thank you all very much for your input. I still think that after 53 years of rotational stress from the brakes and the vertical stress these bolts endured, they just gave it up and snapped.

Anyways I replaced those shoulder bolts on the passenger side as well as the drivers side along with the brake hoses. Well, that's one for you guys with the closed knuckle dana 44.