Driveshaft Length 8” to 9” Rearend Swap

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Chopaka
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Driveshaft Length 8” to 9” Rearend Swap

Post by Chopaka » 16 Dec 2017, 15:09

What is the correct driveshaft length for a 1967 390 4 speed Cougar.The car had an 8” rearend I swapped for the correct 9”,the driveshaft is now to long to bolt in.I will get it shortened but would like to know the correct length.Any help would be greatly appreciated.Thanks

Cougar Bill
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Re: Driveshaft Length 8” to 9” Rearend Swap

Post by Cougar Bill » 17 Dec 2017, 11:09

You should be able to get the correct length by measuring from the end of the trans to the center line of the rear u-joint cap / center of the rear yolk. I just had one made for a customers 69 351W. Got a new yolk, 2 u-joints (Spicer) & the drive shaft was made & balanced w/ new tube steel. All for under $200
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Trixie
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Re: Driveshaft Length 8” to 9” Rearend Swap

Post by Trixie » 17 Dec 2017, 12:23

Correct length is 53 1/32" Measured from the center line to center line of the u-joint mounting. (on the shaft)
I would double check this by measuring before doing any shortening. This measurement is for the shaft only
It does not include the yolk or any other attaching parts.
This is only my advice, I will not be held responsible for any errors.
Dave & SuAnn Harty
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allenman85
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Re: Driveshaft Length 8” to 9” Rearend Swap

Post by allenman85 » 17 Dec 2017, 19:58

What's with all the eggs underneath your cars?
Cougar Bill wrote:
17 Dec 2017, 11:09
Got a new yolk
Trixie wrote:
17 Dec 2017, 12:23
It does not include the yolk or any other attaching parts.
I suspect they mean yoke (not yolk) -- and if you use the same dimension yoke you do not have to change lengths. However there are 3 to 4 length yokes that can be mated with a 9". Correct driveshaft length should only be determined after install.
1970 Cougar. 351C/FMX/AC/PS/PB/Comp Green w/White Top, 3:00 open
Now: 622 HP, 351W w/AFR, solid roller, 418ci, C6, 3.50:1 posi, 3" Magnaflow SS exhaust

Chopaka
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Re: Driveshaft Length 8” to 9” Rearend Swap

Post by Chopaka » 18 Dec 2017, 00:35

Thanks for the info.It appears I will need to get a new driveshaft as the one I have now is 2 3/4” inch dia. and has smaller u-joints than what the 9” is set up for.I have a local shop that will be able to fabricate a new one.The old one will be for sale if anyone needs it.

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