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Discussion Starter #1
My cougar has an open rear end. I would like put a posi rear end or some sort of locker system in it. I was just wondering what would be the best one to go with?

thanx
 

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Probably the easiest and cheapest thing to do would be to install the 9" rear axle assembly from a 69-70 Cougar unless your car is a big block '68 in which case it already has a 9" rear axle.

Either way the Detroit Locker differential is the best one available regardless of price; it also costs less than most units available.

The differential assembly is available from :
http://www.summitracing.com

You can put a locking differential in an 8" rear but it will cost more and be weaker.
 

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Discussion Starter #3
actually in all honesty, the 8inch is just as strong as the 9 inch and 100lbs lighter. Alot of the internals in the 8 inch are the same peices used in the 9, like spider gears and side gears. Just check out this article at ford muscle http://66.96.130.106/archives/1999/12/lockright/index.shtml
I greatly appreciate the help, i will probably put a detroit locker into it because of how well known it is and it comes highly recommended.

thanx
 

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I think the 9" is about 15 pounds heavier than the 8". The welded housing assembly is 5 pounds heavier, the center section 10 pounds heavier. If 31 spline axles are used add another 2 pounds. Max difference can be 17 pounds in that case.

I am not aware of any Detroit Lockers made to fit an 8" rear. Where did you find that information?
 

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How difficult would it be to switch out the entire 8 inch open diff pumpkin for an 8inch posi/locker, is that the easiest route to go?
 

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It would be easy but probably cost would be about the same as installing a complete 9" rear.
 

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From reading the article, I believe they are implying the entire rear-end would be 100 pounds lighter. However, I don't see how this could be. I'm with Royce, the center section probably isn't more than 15 or so pounds lighter. As for the housing itself, have you ever lifted a 8 or 9 inch housing, without axles or pumpkin installed? There is nothing to it. And, the axles are common between both setups. 100 lbs, I don't think so...
 

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Having changed many 8" and 9" center sections, I have to agree with 15-20 lb estimate. I don't know where FordMuscle came up with 100 lbs, they are usually very good about such things. :confused:

As far as the power trax posi unit - It installs easy, worst thing is setting up the gears again. This is made a lot easier if you are using the same gears. :)
 

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Discussion Starter #11
So if i do go to a 9" rear end, do i have to change the housing to or can i just swap pumpkins and internals?
 

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You have to swap housing and all.
My father has an AUburn posi in his 8" 66 Mustang and loves it. It is a clutch type. It's doubtful that you would need a 9" with a small block. I would swap to 9" only if you had a complete one at a reasonable price.
 

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Use the link in my earlier post to go to Drive Train Specialists. They list the Auburn for the 8". Around 430 I think. Summit or Jegs may have them as well - I believe I have seen them in Jegs catalogs.
 

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I don't have anything at all to contribute, but it's pretty much impossible for me to NOT look at a thread with a title like this one...

Alas, things are never as they appear, are they ;)
 

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:lol2:
 

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Discussion Starter #18
What vehicles would i find a 9" trak lok or even and 8" for that matter. i know some older fords came with an 8" trak lok.
 

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8" was used in 6 cyl and small block Mustangs and Mustang II through 74 I believe. How many of them were locking? Probably none. I don't think Ford offered a locking 8" from the factory. Locking 9" is no easy find now a days either. For a 9" I would look in pickup trucks.
 

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The 8" rear was used at least until 1978 in the Mustang II, Granada, Mercury Monarch, Maveric and Comet. Posi's were a factory option from 1963 until 1978 in 8 inch rears but they were extremely rare. I have seen a lot of rare and unusual things in all the Cougars, Mustangs, Falcons and Comets I have owned but none had a posi.
 
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