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Discussion Starter #1
Looks like I will be swapping the 8" rear in my 67 to a 9" from a 70. Anyone have the link to a list with the length measurements for different years ?
I lost my old links when my PC died.

Can I use the same drive shaft on the 9" ?

Thanks!
 

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Rear end is the same with. Not sure about the drive shaft. It will probably be longer than you need.mm
 

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Discussion Starter #3
thanks Mark. Wonder if the 70 shaft would work on mine?
If it is 70 I can guess 351/FMX. Prolly different than my C4.
 

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Rear end is the same lenght, but the spring perches are in a different location, be prepared to move them if you have too.

Rick
 

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8 inch

Hi,
I have a similar question. My parts car is a 65 Fairlane with an 8 inch rear. Just found out its a posi also. So will it fit? The widths are listed as the same, but how about the spring perches. I'd go look, but both cars are far, far away :(
 

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Just thought of something...could I just swap the carriers?
 

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Discussion Starter #8
Thanks for the link Rick.
The perch is the plate welded to the axle tube right?

Do you mean have the perch welded to a different location?
 

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Kirkm76: The center sections (pumpkins) should interchange as long as you have the same number of splines on the axles. I know that 9" rearends came with either 31 or 28 spline axles. I do not know if 8" rears had the 2 different axles or not, but as long as the axles are the same type the pumpkins will interchange.
 

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You can swap centers, and the yoke might even be the same, so you can use your same shaft.
Thats alot easier then cutting off the perches, and welding on NEW ones.

Rick
 

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9 inch swap

The spring perch location is the same for all 1967 - 1970 Mustangs and Cougars.

Royce Peterson
 

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Discussion Starter #12
Whoohoo! thanks Royce. I dont have a welder (wish list) so I was hoping I wouldnt have to cut and weld.

What should I about the shaft? Could this be an excuse for an aluminum shaft? :D
 

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Drive shaft

There were a couple different styles of yoke on 1969 - 70 9 inch center sections, depending on which yoke you have it might just bolt up. There are certain yokes that would require the driveshaft to be shortened an inch or so.

Royce Peterson
 

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Don't forget about u-joints!

Don't forget about the small/large U-joint issue!

Most small block powered cars will have the small u-joints, whereas big block cars (and some stickshift small blocks) will have the large u-joints. You can swap the yoke on the rearend pig rather easily to the one you want, just don't overtighten it or you'll mess up the bearing preload.

Then there's the yoke length issue.... some are longer than others. Most driveline shops can cut, weld and rebalance your driveshaft for a nominal fee. The last time I checked it was about $35. That's a heck of a lot cheaper than making up a new shaft!
 

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hmm, you want the driveshaft too?? to be honest im not sure if the car has it at all , but ill take a look once i can get it to school and begine the ripping apart of it all. ill take pics and save the VIN plate as a reminder of the car he he.
 

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Discussion Starter #16
uh, idunno. I'd bet it has (or had) a FMX. hmm. need to find out about driveshaft differences.

is the FMX different size than a c4? anyone?
 

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I'v got a 9" and Iwas woundering how to find out what spline it is? I do have it all apart but the tag has long since been lost.
 

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The splines refer to the number of "teeth" on the end of the axle shaft. To be sure, you should count them, or if the axles aren't available, count the teeth where the axles go into the rear end's center section.
A dirty and not absolutely positive way to tell is to look at the rear end housing. This is useful if you don't have a tag and cannot take the rearend apart: If the axle shafts taper down at the wheel end it is a 28. If they are the same diameter from brake drum to center section than it "should be" a 31 - but "could be" a 28 since they will fit. The 31's are too fat and will not slide into the tapered housing.
 
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