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Driveshaft spacer

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Driveshaft spacer

Postby John@RED » Sat Nov 26, 2016 2:08 pm

Hi, for some reason I'd need to add a 0.5" spacer between driveshaft to rear diff round flanges.
These flanges are bolted through #4 M10 bolts: is it ok to use longer bolts there to suit the spacer?
Is it going to be a weak point in a high torque engine?
Thanks
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Re: Driveshaft spacer

Postby pdq67 » Sat Nov 26, 2016 6:55 pm

I would think that Grade-8 bolts would be fine here.

Just make sure to torque them as required.

I would not hesitate for a minute to use GM's 300M type bolts if I could get them in the needed size because imho, 300M is tough as nails!!

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Re: Driveshaft spacer

Postby Rizzle » Sat Nov 26, 2016 7:03 pm

What application? Its the trans/ transfer case / large tires vs say a pg street car type of issue. Throw a 4:1 1st and a 3:1 TC reduction, and even a 160ft/lb 4-banger ends up being 'high torque'. (1900ft/lb for my example).
But, if the center is located on the spacer for both the flange and the the shaft flange, the only job the bolts need to do is to clamp so as to let the friction do the work. If it is legitimately high torque, consider a dowel or two between the flanges and the spacer.
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Re: Driveshaft spacer

Postby peejay » Sun Nov 27, 2016 9:37 am

People put through-spacers on axleshafts all the time, and they are held in with six 8mm bolts and see a lot more torque.

I wouldn't think twice about it.

The friction ALWAYS holds things in place, but you will need to have pilots on both sides of the spacer to ensure the driveshaft isn't installed off-center.
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Re: Driveshaft spacer

Postby John@RED » Tue Nov 29, 2016 9:42 am

Thanks guys,
yes, the spacer will need a male/female step, as there is on the ds/diff flanges, to center it.
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Re: Driveshaft spacer

Postby Speedbump » Tue Nov 29, 2016 12:56 pm

Another thing I think is worthwhile is to make a special bolt length to do the job. I select the bolt based on shank dimension so the flanges and spacer holes are almost all filled with bolt shank, which is stronger and fits better, with only enough thread to properly engage the nut of choice and I NEVER use a lock washer in that type of application. It mostly requires cutting some of the thread end off and dressing the threads for the proper overall length. Aircraft folks have designed and used this type of bolt for years, mostly in SAE threads, but you can make your own with a little effort.
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Re: Driveshaft spacer

Postby John@RED » Tue Nov 29, 2016 1:39 pm

Speedbump wrote:Another thing I think is worthwhile is to make a special bolt length to do the job. I select the bolt based on shank dimension so the flanges and spacer holes are almost all filled with bolt shank, which is stronger and fits better, with only enough thread to properly engage the nut of choice and I NEVER use a lock washer in that type of application. It mostly requires cutting some of the thread end off and dressing the threads for the proper overall length. Aircraft folks have designed and used this type of bolt for years, mostly in SAE threads, but you can make your own with a little effort.


Ok, thanks!
May I ask you why no lock washer? If've seen Toyota puts lock washers under the bolt and not under the nut...
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Re: Driveshaft spacer

Postby Speedbump » Wed Nov 30, 2016 10:20 am

I'm not an engineering type but, to me, a lock washer is a hard piece of metal designed to dig into the parent metal to prevent turning. On a hard bolt, there is little of the digging so the lock washer doesn't serve it's intended purpose and becomes another, unneeded springy spacer to work loose. I prefer red or blue Loctite and, if anything, a hardened flat washer to help with proper torque which is really what keeps a bolt/nut tight. It's just my opinion here but you seldom see ARP or other quality bolt makers send lock washers with their specialty fasteners like flywheel bolts, and those serve close to the same function as what you are doing. You never see them in the aircraft business either. Other opinions may differ.
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Re: Driveshaft spacer

Postby cgarb » Tue Dec 13, 2016 2:03 am

I made a spacer for my 8.8 and used allen head cap screws with no problems, mine was a 1/2 inch thick also. Male, and female fits as described above. Used it to crutch my old driveshaft till I could get funds together to order the aluminum 1350 yoke shaft.
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