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Thread: 2015+ Super 8.8 Non Performance Pack vs Performance Pack Rear Ends

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    2015+ Super 8.8 Non Performance Pack vs Performance Pack Rear Ends

    Hello All,

    I am in the process of planning and saving to order a coupe this fall and I am trying to track down a rear end and I was wondering are there differences (beyond gearing) between the 3.73 performance pack rear ends and the non performance pack rear ends?

    Thank you
    Ted

  2. #2
    Senior Member Clover's Avatar
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    Yes, they are a different styles of limited slip differentials. The 3.73 in the Performance Pack is a Torsion differential while the rest are Trac-Lock or something like that. Also, the center section with the lowest gear ratio can't be changed while the higher ratios gears can be replaced for different ratios. Lastly, some center sections have aluminum covers and others are steel. I think the weight difference is about 20lbs. To my knowledge, nobody with a Factory Five has broken an aluminum center section but Ford did make a stronger version for a reason.

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    Senior Member edwardb's Avatar
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    Quote Originally Posted by Clover View Post
    Yes, they are a different styles of limited slip differentials. The 3.73 in the Performance Pack is a Torsion differential while the rest are Trac-Lock or something like that. Also, the center section with the lowest gear ratio can't be changed while the higher ratios gears can be replaced for different ratios. Lastly, some center sections have aluminum covers and others are steel. I think the weight difference is about 20lbs. To my knowledge, nobody with a Factory Five has broken an aluminum center section but Ford did make a stronger version for a reason.
    Close. The super 8.8 center section is available in 3.15, 3.31, 3.55 and 3.73 ratios. As mentioned, the 3.15 gearing can't be changed. The others can. The 3.73 version has a Torsen gear based limited slip setup. The rest are the more traditional Ford Trac-Lok clutch disk setups. The Torsen is nice and in some cases a more desirable setup. But it's also twice as expensive, and no longer sold by Ford Performance. Salvage is the only option, or change out the clutch packs. The Torsen unit itself is available (https://performanceparts.ford.com/part/M-4204-MT) and can be retrofitted to other ratios except 3.15 as mentioned. Ford uses aluminum cases (not the cover) on automatic shift cars and iron cases on manual shift. Agreed about a 20 pound weight difference. All have aluminum back covers. The concern with the aluminum case is the front mounting ears breaking off. Initially, Factory Five only recommended the iron case version. But later changed to saying either is OK. Agreed there haven't been any reported examples of the aluminum case breaking and probably won't. These super 8.8 diffs are very robust, especially for our builds.

    Note if you have Factory Five supply the center section as an option, they have been providing the NIB Ford Performance version, which is an iron case 3.55 with Trac-Lok. There are lots of these available in salvage now, and if you shop carefully there are deals to be had. I've done both. Bought one from salvage (found one with zero miles) and NIB.
    Last edited by edwardb; 06-14-2018 at 09:14 AM.
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    Thanks guys!

    Ya I am leaning towards a low miles savage Performance pack rear end. How much can the Trac-loks handle as far as power?

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    Senior Member edwardb's Avatar
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    Quote Originally Posted by T6Ted View Post
    Thanks guys!

    Ya I am leaning towards a low miles savage Performance pack rear end. How much can the Trac-loks handle as far as power?
    Unless you're talking about high horsepower (and I'm talking about ridiculous numbers) and drag slicks really nothing to be worried about IMO. The Mustang crowd is running this diff with big power adders and sticky tires basically unchanged other than stiffer mounts. A much heavier car of course. And the Factory Five mounts are poly and already pretty stiff. Axles are what the Mustang guys are breaking. But again, unless you're talking crazy numbers, the ones Factory Five provides are very strong for these builds.
    Last edited by edwardb; 06-14-2018 at 10:46 AM.
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    Quote Originally Posted by edwardb View Post
    Unless you're talking about high horsepower (and I'm talking about ridiculous numbers) and drag slicks really nothing to be worried about IMO. The Mustang crowd is running this diff with big power adders and sticky tires basically unchanged other than stiffer mounts. A much heavier car of course. And the Factory Five mounts are poly and already pretty stiff. Axles are what the Mustang guys are breaking. But again, unless you're talking crazy numbers, the ones Factory Five provides are very strong for these builds.
    I suspected that was the case with the Trak-Loc. I am putting a 427W in my coupe so 500-600hp. From my initial search of complete rear ends its only a couple hundred difference between Perf pack and non so likely just focus on finding a 3.73 rear end.

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    Senior Member Clover's Avatar
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    Would you let me know where you are finding the Perf pack rear ends? I have been looking but am not really finding much. As edwardb said, Ford Performance stopped selling them and the other venders I checked seem to have sold off their stock.

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    Senior Member edwardb's Avatar
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    Quote Originally Posted by T6Ted View Post
    I suspected that was the case with the Trak-Loc. I am putting a 427W in my coupe so 500-600hp. From my initial search of complete rear ends its only a couple hundred difference between Perf pack and non so likely just focus on finding a 3.73 rear end.
    Just make sure you look at the whole picture when deciding about the diff ratio. Engine, trans, diff, wheel size, how you're planning to use the car. Depending on the trans you're planning, along with everything else, with power like that 3.73 might be on the high side. Play with the numbers using a calculator like this one http://www.tremec.com/calculadora.php. Understand you may want to use the Torsen setup. But that's where guys are swapping out the clutch packs for the Torsen in the 3.31 or 3.55 diffs where it makes sense. Or swapping the gears in a 3.73 Torsen. Either works.
    Last edited by edwardb; 06-14-2018 at 02:19 PM.
    Build 1: Mk3 Roadster #5125. Sold 11/08/2014. Build 2: Mk4 Roadster #7750. Sold 04/10/2017. Build Thread
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  10. #9
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    Yea make sense. But being an auto engineer I do love Excel! But you were not far off. Looking like 3.73 gearing will work. For starters 4.11 with the 2.66 1st gear in the close ratio T56 is 10.93. Making for a bit of a rough cruiser. With the 3.73 dropping it down to 9.93 that is a little bit more livable as my goal is a hybrid track/cruiser. Leaning towards track/race car really.



    Gearing.PNG

  11. #10
    Senior Member edwardb's Avatar
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    Quote Originally Posted by T6Ted View Post
    Yea make sense. But being an auto engineer I do love Excel! Looking like 3.73 gearing will work. For starters 4.11 with the 2.66 1st gear in the close ratio T56 is 10.93. Making for a bit of a rough cruiser. With the 3.73 dropping it down to 9.93 that is a little bit more livable as my goal is a hybrid track/cruiser. Leaning towards track/race car really.
    I'm not quite getting your reference to 4.11, since that's not an available diff ratio. If that's what you meant. But the 3.73 and T-56 Magnum with the 2.66 first (Tremec TUET11010) matches up quite nicely. Happens to be the combination I'm using in my Gen 3 Coupe build. Very similar in a lot of ways with a TKO600 and 3.55, which is a very popular combination and I have in my Roadster.

    Quote Originally Posted by T6Ted View Post
    But you were not far off.
    Thanks. I think.
    Build 1: Mk3 Roadster #5125. Sold 11/08/2014. Build 2: Mk4 Roadster #7750. Sold 04/10/2017. Build Thread
    Build 3: Mk4 Roadster 20th Anniversary #8674. Sold 09/07/2020. Build Thread and Video. Build 4: Gen 3 Type 65 Coupe #59. Gen 3 Coyote. Legal 03/04/2020. Build Thread and Video
    Build 5: 35 Hot Rod Truck #138. LS3 and 4L65E auto. Rcvd 01/05/2021. Legal 04/20/2023. Build Thread. Sold 11/9/2023.

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