Another NA car breaks diff bolts...

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ponie1992

ponie1992

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I would check the markings on the heads to be sure they didn't send the wrong bolts. Hard to believe you broke a 10.9 !
Rebuild it to run longer and stronger.
Some guys have broken the 12.9 bolts.
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ponie1992

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Threw bolt design is very involved if your not pulling diff already, you need room to drill out the threads in the front bushing mounts for threw bolts, I think I’ll just up grade to the 12.9 hardware kit from BMR, Steeda if they have it.... this is bullshit BMR wouldn’t use the 12.9 hardware anyway with their bushing inserts, they’ve known about this problem for a long time now
I'm gonna drop the entire cradle anyway, so I'll have everything right in front of me and easily accessible. I agree, this kit should have the upgraded bolts to begin with.
 
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ponie1992

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I wonder if the factory setup would have broke. I'm thinking the inserts caused the added shear stresses on the bolts.
It's possible the stock bushings may have absorbed some of the shock, but I have heard of guys breaking the stock bolts with stock bushings as well.
 

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auto swap????
 

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I will say this. With few exceptions, race cars don't do burn-outs on hot tires. If they do, there are a lot parts getting lifed out before they break. This was his 4th launch in a few minutes. The tires were warm enough to be pretty sticky and that concrete had some grip on it. There is a huge drivetrain load with dropping the clutch and accelerating the wheels/tires to whatever speed almost instantly. That load is increased by getting the tires warm and sticky. When you see a car on TV leave pit road with a big, smoky burnout, that's on cold tires that still have mold release on them. If double-stinting the tires, the pit-box launch is much more controlled.

Do what you want to do, but clutch drops are pretty abusive.
 

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It's possible the stock bushings may have absorbed some of the shock, but I have heard of guys breaking the stock bolts with stock bushings as well.
For sure, the stock bushing will allow more deflection and soften the impulse of the burn-out. This will lower the peak load, but the load will be spread out over a longer time duration.
 

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forget the bolts. cut the stupid-ass Ford bushings out and replace with Whiteline's kit. Why the 'puck' kits don't include the reducer collar I don't know - would seem to be an obvious item.
 

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I wonder if the factory setup would have broke. I'm thinking the inserts caused the added shear stresses on the bolts.
This is a possibility
 

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forget the bolts. cut the stupid-ass Ford bushings out and replace with Whiteline's kit. Why the 'puck' kits don't include the reducer collar I don't know - would seem to be an obvious item.
Reducer collar? Any pics?
 

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just one example. There are at least 3 companies offering this. I'm talking about the top left/right item. It reduces the 16mm hole in the Ford bushing to 14mm to match the dia of the bolt. It's a mind-blowing catastrophic error by Ford engineering which apparently they can't be arsed to fix in 5 years. I wonder if the GT500 got a correctly designed part.

http://m.bmrsuspension.com/?page=products&productid=1764
 

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just one example. There are at least 3 companies offering this. I'm talking about the top left/right item. It reduces the 16mm hole in the Ford bushing to 14mm to match the dia of the bolt. It's a mind-blowing catastrophic error by Ford engineering which apparently they can't be arsed to fix in 5 years. I wonder if the GT500 got a correctly designed part.

http://m.bmrsuspension.com/?page=products&productid=1764
Gotcha. I run that kit along with the insert kit.
 

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For me personally, the ideal setup would be stock bushings with the aftermarket hardware/collars. That said, I have the white line kit and it’s fine but there is NVH that can be annoying on long drives.
 
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ponie1992

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I will say this. With few exceptions, race cars don't do burn-outs on hot tires. If they do, there are a lot parts getting lifed out before they break. This was his 4th launch in a few minutes. The tires were warm enough to be pretty sticky and that concrete had some grip on it. There is a huge drivetrain load with dropping the clutch and accelerating the wheels/tires to whatever speed almost instantly. That load is increased by getting the tires warm and sticky. When you see a car on TV leave pit road with a big, smoky burnout, that's on cold tires that still have mold release on them. If double-stinting the tires, the pit-box launch is much more controlled.

Do what you want to do, but clutch drops are pretty abusive.
No argument there. I was thinking this added to what happened. Tires are Michelin Pilot Super Sports.
 
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ponie1992

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just one example. There are at least 3 companies offering this. I'm talking about the top left/right item. It reduces the 16mm hole in the Ford bushing to 14mm to match the dia of the bolt. It's a mind-blowing catastrophic error by Ford engineering which apparently they can't be arsed to fix in 5 years. I wonder if the GT500 got a correctly designed part.

http://m.bmrsuspension.com/?page=products&productid=1764
This upgrade bolt kit should just come standard with the poly inserts. They do make more money selling them separately though lol.
 
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