Diff cover bolts? Anyone try using grade 12.9 bolts

[PunksJL]

I received my Dana 44 AdvanTEK differential covers and am planning my install. I'm a bit concerned about the torque specs on the included grade 10.9 bolts. Dana specifies 28 - 33 ft./lbs. but some have reported the bolts breaking well before that amount of torque is applied. I found these 12.9 grade fasteners online and wonder if they would be a better choice? Most grade 12.9 hardware is 12 point or hex cap type. Has anyone used these or something similar they would recommend?

M8-1.25 x 25mm 12 Point Flange Bolt, Cl 12.9 | AFT Fasteners

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[The Last Cowboy]

I can't even imagine a 12.9 breaking at 33 ft lbs. The max torque on it is 48.3 lbs for the M8. Max torque for the 10.9 M8 is 41.5 ft lbs. Those who break them must not be using a torque wrench. Cant go wrong with e 12.9 fasteners though. Cheap insurance. And if someone over tightened the old 10.9s in the past, they will need to be replaced anyway.

 

[oceanblue2019]

The issue with people breaking them is they have oil on the threads. The lubricated torque for a M8 10.9 is 24 ft/lb. Dry is 30 ft/lb. Torque to 30 ft/lb wet is beyond failure point. Or go to 12.9 if you like but also note 28 ft/lb lubricated, 35 ft/lb dry.

 

[The Last Cowboy]

Always put them in dry. If they wont thread easy, run a tap in the hole to clean the threads out. Junk at the bottom of the hole, effectively reduces it's depth, and can cause sealing issues and temptation to over tighten.

 

[PunksJL]

The issue with people breaking them is they have oil on the threads. The lubricated torque for a M8 10.9 is 24 ft/lb. Dry is 30 ft/lb. Torque to 30 ft/lb wet is beyond failure point. Or go to 12.9 if you like but also note 28 ft/lb lubricated, 35 ft/lb dry.

Very interesting. Thank you for responding. I don't think I've ever seen torque tables from vehicle manufacturers specifying distinct wet and dry torque values. In my search for hardware online I have not noted this as well. It makes sense what you are saying though. The bolts that came with the AdvanTEK covers seem to have a thread locker material already applied. Would using a thread locker such as Permatex Blue be considered a lubricant and torqued to 24ft/lb?

 

[PunksJL]

I can't even imagine a 12.9 breaking at 33 ft lbs. The max torque on it is 48.3 lbs for the M8. Max torque for the 10.9 M8 is 41.5 ft lbs. Those who break them must not be using a torque wrench. Cant go wrong with e 12.9 fasteners though. Cheap insurance. And if someone over tightened the old 10.9s in the past, they will need to be replaced anyway.

The supplied bolts are class 10.9. They are the ones people have reported breaking.

 

[oceanblue2019]

Very interesting. Thank you for responding. I don't think I've ever seen torque tables from vehicle manufacturers specifying distinct wet and dry torque values. In my search for hardware online I have not noted this as well. It makes sense what you are saying though. The bolts that came with the AdvanTEK covers seem to have a thread locker material already applied. Would using a thread locker such as Permatex Blue be considered a lubricant and torqued to 24ft/lb?

Lubricated/dry torque values is very common for engine assembly. ARP has several videos on this. The higher the torque value the more lubrication becomes a factor.

The diff cover bolts, especially the lower ones, typically have oil in them from draining the diff. This does impact torque significantly as outlined above.

Is the thread locker in liquid form or has it been dried on the threads already? If dry it is a none-factor and use the dry torque values.

 

[oceanblue2019]

FYI: https://blog.hydrostatic-transmission.com/2016/04/06/john-deere-metric-bolt-cap-screw-torque-values/

 

[azwjowner]

I've always torqued diff cover bolts to 25 ft-lbs and never had one loosen or leak. No reason to ever go more. If you buy bolts, remember to add the additional thickness of your Dana cover to the length of the bolts.

 

[PunksJL]

Lubricated/dry torque values is very common for engine assembly. ARP has several videos on this. The higher the torque value the more lubrication becomes a factor.

The diff cover bolts, especially the lower ones, typically have oil in them from draining the diff. This does impact torque significantly as outlined above.

Is the thread locker in liquid form or has it been dried on the threads already? If dry it is a none-factor and use the dry torque values.

The supplied bolts have a type of pink thread lock which is dry to the touch. These are the bolts that people have reported snapping.

 

[PunksJL]

FYI: https://blog.hydrostatic-transmission.com/2016/04/06/john-deere-metric-bolt-cap-screw-torque-values/

Awesome! Thank you for providing this!

 

[oceanblue2019]

The supplied bolts have a type of pink thread lock which is dry to the touch. These are the bolts that people have reported snapping.

I would just torque those to 24 ft/lb and call it done. They won't back out due to the threadlock and plenty of clamping force to not leak.

 

[oceanblue2019]

Also FYI - I would not go to 12 point heads. Means extra tools needed on the trail to repair. Not likely to find someone with 12 points. If you do make sure you toss the right one in the trail toolkit.

 

[PunksJL]

Also FYI - I would not go to 12 point heads. Means extra tools needed on the trail to repair. Not likely to find someone with 12 points. If you do make sure you toss the right one in the trail toolkit.

Based on your advice, I think I'm just gonna give these a try at 24 ft/lbs. Thanks again.

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