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Thread: Finally got the diff in!

  1. #1
    Join Date
    Apr 2005
    Posts
    723

    Finally got the diff in!

    I was hoping to be further along than this by now, but im happy to at least be working on the car.


    I spent a lot of time cleaning under there with kerosene and a rag. The original diff was slinging oil everywhere for a long time.


    Here is the difference between long and short tab clutches.


    And, short tab will work. I used the clutch and spring kit for 03-04 cobra 109.00 shipped from summit.


    The original iron case fully assembled was 74#.


    The aluminum casefully assembled was 56#. Not as much difference as i thought it would be.

    Another difference i found was the cross pin and pinion gears size. Usually i would buy a Auburn Pro and use it. But, jm going cheap so i threw this together out of parts i had. It looks like the fn10/mn12 cars use a wimpy cross pin and pinion gears set up. I found this out by accident when i tried to use pin and pinion gears from a f150. They wouldnt fit in the track lock body from my cougar. The original pin was badly gauled to the point that it blued one of the pinion gears. So, i just used a pin and gears out of an open diff from a mark viii i had on the shelf.

    Oh, whats the deal with the axle shafts? I thought someone here told me the mark viii axles were tougher. The shafts for an SC have way more meat on them. The only thing i can see better about the mark viii shafts is on the out board joint there is a nice transition fromm the splines to the joint. I figure it would make the outboard joint stronger. But, the shaft is so much narrower.

  2. #2
    Join Date
    Jul 2002
    Location
    Manchester, NH
    Posts
    2,064
    Quote Originally Posted by HwyStar View Post
    Another difference i found was the cross pin and pinion gears size. Usually i would buy a Auburn Pro and use it. But, jm going cheap so i threw this together out of parts i had. It looks like the fn10/mn12 cars use a wimpy cross pin and pinion gears set up. I found this out by accident when i tried to use pin and pinion gears from a f150. They wouldnt fit in the track lock body from my cougar. The original pin was badly gauled to the point that it blued one of the pinion gears. So, i just used a pin and gears out of an open diff from a mark viii i had on the shelf.
    Maybe the difference in the cross pin size has to do with the spline size as well. I know the F150 is a 31 spline differentials and I beleive ours are 28. I know the 01 and up Cobra's are 31 spline but for some reason I think our differentials use 28 spline axles.

  3. #3
    Join Date
    Apr 2005
    Posts
    723
    Not sure why we use 28 spline either. But, if i known better before i put the ring gear on i would have used the f150 carrier and used the sc side gears. That way i could have used the beefy pin and bigger pinon gears. Bottom line, not all 8.8s are same! I had to learn
    Last edited by HwyStar; 01-21-2013 at 02:35 PM. Reason: messed up

  4. #4
    Join Date
    Apr 2002
    Location
    Imperial, MO (near St. Louis)
    Posts
    4,331
    Quote Originally Posted by HwyStar View Post
    Oh, whats the deal with the axle shafts? I thought someone here told me the mark viii axles were tougher. The shafts for an SC have way more meat on them. The only thing i can see better about the mark viii shafts is on the out board joint there is a nice transition fromm the splines to the joint. I figure it would make the outboard joint stronger. But, the shaft is so much narrower.
    The FN10 shafts are supposedly hardened. Regardless, the middle shaft (where the extra meat is on the SC shafts) isn't what breaks. The stub shafts at the ends, typically the hub end, is where the breakage almost always occurs.

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