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Thread: Half Shafts

  1. #16
    Join Date
    Nov 2004
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    butler pa
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    1,926
    I am using stock SC replacements from Advance Auto. they have held up to hundreds of trans-braked launches with no failures. I am actually very surprised on how well they are doing!

  2. #17
    Join Date
    Apr 2002
    Location
    St. Charles, MO
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    21,070
    Kevin,

    Is your car back together and running again ?

    David
    1991 SC AOD 4.2..2.3 Whipple..........10.910 @ 125.61
    2016 SRT Challenger Hellcat.............10.597 @ 135.78

    My Garage

  3. #18
    Join Date
    Nov 2003
    Location
    Virginia
    Posts
    99

    Wink Ok I'll let the cat out of the bag!

    Guys, I've been running the Level 5 Cobra axles for two months. You need to switch over to a 31 spline diff to make it work though. The MN12 axles assembled length is 5/8" longer than the 03 Cobra axle. This length can be made up in setting the assembled length a little longer on a stock Cobra axle. On the Level 5 axles it's a matter of assembling the inner tri pod like a stock cobra axle instead of the way the Drive Shaft shop does the Cobra setup. I've done a couple sets.

    I need to see if the inner 28 spline MN12 tri pod joint will mate to the stock Cobra half shaft. If it does This would be another avenue for a upgrade. If you are rebuilding the rear anyway, swapping to a 31 spline diff is not to expensive, and a set of new 03 Cobra axles is about the same cost as a set of Raxles.

    Mike.....

  4. #19
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    Nov 2004
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    butler pa
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    1,926
    Quote Originally Posted by David Neibert
    Kevin,

    Is your car back together and running again ?

    David
    I finially got everything back from AJE after 2 wrong K-members and 1 wrong set of struts. hopefully a couple of weeks.

  5. #20
    Join Date
    Aug 2004
    Location
    Batavia,OH
    Posts
    2,019
    I'd beware of markVIII shafts from alot of places as most people belive they are the same as standard thunderbird axles. From what I have been told the markVIII axles have a better outer section where they connect to the wheel bearing and I know for sure that they are slightly thicker than standard thunderbird axles.
    Alan

  6. #21
    Join Date
    Jul 2002
    Location
    Ohio
    Posts
    863
    Quote Originally Posted by EECDOC
    Guys, I've been running the Level 5 Cobra axles for two months. You need to switch over to a 31 spline diff to make it work though. The MN12 axles assembled length is 5/8" longer than the 03 Cobra axle. This length can be made up in setting the assembled length a little longer on a stock Cobra axle. On the Level 5 axles it's a matter of assembling the inner tri pod like a stock cobra axle instead of the way the Drive Shaft shop does the Cobra setup. I've done a couple sets.

    I need to see if the inner 28 spline MN12 tri pod joint will mate to the stock Cobra half shaft. If it does This would be another avenue for a upgrade. If you are rebuilding the rear anyway, swapping to a 31 spline diff is not to expensive, and a set of new 03 Cobra axles is about the same cost as a set of Raxles.

    Mike.....
    Mike, I'm VERY interested in this as I know that the 31 spline is tougher and will handle more. Since I need a Diff anyways and I'm probably doing the Cobra hub swap as well, this seems to make sense to me to just do the ENTIRE swap. Please PM me with more details. I can kind of visualize what you are talking about, but since I've never set-up a set of half-shafts, I'm not totally sure as to what you are talking about.

    -Josh

  7. #22
    Join Date
    Apr 2002
    Location
    Karns, TN
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    1,328
    Quote Originally Posted by EECDOC
    Guys, I've been running the Level 5 Cobra axles for two months. You need to switch over to a 31 spline diff to make it work though. The MN12 axles assembled length is 5/8" longer than the 03 Cobra axle. This length can be made up in setting the assembled length a little longer on a stock Cobra axle. On the Level 5 axles it's a matter of assembling the inner tri pod like a stock cobra axle instead of the way the Drive Shaft shop does the Cobra setup. I've done a couple sets.

    I need to see if the inner 28 spline MN12 tri pod joint will mate to the stock Cobra half shaft. If it does This would be another avenue for a upgrade. If you are rebuilding the rear anyway, swapping to a 31 spline diff is not to expensive, and a set of new 03 Cobra axles is about the same cost as a set of Raxles.

    Mike.....
    Mike, this seems like the best economical setup for the HP cars. Can you give more details in what is exactly needed to complete this change over? I for one am interested in a upgrade like this.

    Mike
    1989 Cougar XR7 - [I]Modified[/I]
    1967 Cougar XR7 - untouched -
    2011 F350 Crew Cab Superduty FX4
    6.7 diesel 435hp/800 ft lbs torque
    2010 Harley Davidson Ultra Classic
    1965 Factory Five Challenge Road Race Cobra

  8. #23
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    Apr 2002
    Location
    St. Charles, MO
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    Quote Originally Posted by EECDOC
    Guys, I've been running the Level 5 Cobra axles for two months. You need to switch over to a 31 spline diff to make it work though. The MN12 axles assembled length is 5/8" longer than the 03 Cobra axle. This length can be made up in setting the assembled length a little longer on a stock Cobra axle. On the Level 5 axles it's a matter of assembling the inner tri pod like a stock cobra axle instead of the way the Drive Shaft shop does the Cobra setup. I've done a couple sets.

    I need to see if the inner 28 spline MN12 tri pod joint will mate to the stock Cobra half shaft. If it does This would be another avenue for a upgrade. If you are rebuilding the rear anyway, swapping to a 31 spline diff is not to expensive, and a set of new 03 Cobra axles is about the same cost as a set of Raxles.

    Mike.....
    Mike,

    Does your new halfshafts still use the 28 spline outer shafts in the hubs ?

    David
    Last edited by David Neibert; 06-27-2006 at 10:56 AM.
    1991 SC AOD 4.2..2.3 Whipple..........10.910 @ 125.61
    2016 SRT Challenger Hellcat.............10.597 @ 135.78

    My Garage

  9. #24
    Join Date
    Nov 2003
    Location
    Virginia
    Posts
    99

    halfshaft setup

    The swap over to 31 spline differential starts with aquiring your choice of trac lok or locker. I'm using a Detroit locker in my car. It is a little harsh for a street car. The Ford truck trac lok or the Auburn pro would be other choices, all of these are offered in 31 spline IRS compatable configuration. These diffs are a bolt in to the 8.8" IRS MN12,FN10,or Cobra housings. Good time to swap ratios too.

    The next step is to chose your axle shaft. You will need a set of stock 03 Cobra axles even if you go with the DSS Level 5 shaft. This is because the Level 5's come minus the inner joint. http://www.driveshaftshop.com/MUSTANGC.V..ivnu
    The link talks about having some inner cv's but that is old info and they can't supply the inner joint. If you watch the Mustang boards for GP's you can get these axles cheaper than the list price. I got mine through D'agostino Racing out of Florida.

    To use the stock cobra axles (31 spline inner, 28 spline like the MN12 outer) It is just a matter of resetting the assembled length of the shaft as outlined in the Thunderbird or 99 Mustang shop manuals. The end to end length of a MN12 axle is 32.565" the end to end length of a Cobra axle is 32.190". The extra length comes from adjusting the plunge of the inner tri pod joint in the inner cv housing. The part number of the cobra axle is 2R3Z-4K138-AA.

    To use the DSS Level 5's, it's a little more involved and more expensive as you need 2 sets of axles to make one. The beauty of these axles are the outer stub shafts. They are huge and 33 spline. They come with a custom hub and long ARP race studs. This forces you to convert to the Mustang bolt circle. The hub swap has been talked about many times so I'll not go into that.

    The extra axle length is easily made up on these axles by the assembley process. The DSS axles use a external snap ring to retain the inner tri pod off the stock Cobra halfshaft. I did not use this, instead I assembled the inner tri pod just like stock using the internal ring and locking the tri pod all the way out on the shaft. The shop manual for the Thunderbird or 99 Mustang show this assembley.

    From there it's a bolt in swap. I also did not use the axle lock nuts supplied by DSS. Instead I used the beefy stock Ford axle nuts that we normally use on the front spindles (the black ones) They torque down nice at 250 ft.lbs.

    Any way that's what I'm running now.

    Mike.........

  10. #25
    Join Date
    Apr 2002
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    St. Charles, MO
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    To use the stock cobra axles (31 spline inner, 28 spline like the MN12 outer) It is just a matter of resetting the assembled length of the shaft as outlined in the Thunderbird or 99 Mustang shop manuals. The end to end length of a MN12 axle is 32.565" the end to end length of a Cobra axle is 32.190". The extra length comes from adjusting the plunge of the inner tri pod joint in the inner cv housing. The part number of the cobra axle is 2R3Z-4K138-AA.



    Mike,

    Thanks for sharing all that info. So all I would need to use the 03/04 cobra halfshafts is 31 spline diff and housing ? Sounds too easy.

    David
    1991 SC AOD 4.2..2.3 Whipple..........10.910 @ 125.61
    2016 SRT Challenger Hellcat.............10.597 @ 135.78

    My Garage

  11. #26
    Join Date
    Apr 2002
    Location
    Karns, TN
    Posts
    1,328
    Do I understand it correctly that the Cobra has 28 spline outboard shafts and they are stronger than the SC outboard 28 spline shaft? From what I have read the most common breaking point on the SC is in the outboard shaft regoin. Will this swap help us in that area or only in the other areas?

    Mike
    1989 Cougar XR7 - [I]Modified[/I]
    1967 Cougar XR7 - untouched -
    2011 F350 Crew Cab Superduty FX4
    6.7 diesel 435hp/800 ft lbs torque
    2010 Harley Davidson Ultra Classic
    1965 Factory Five Challenge Road Race Cobra

  12. #27
    Join Date
    Nov 2003
    Location
    Virginia
    Posts
    99

    Cool

    David, the swap over to 31 spline IRS axles requires changing the ring gear carrier to a unit that has 31 spline IRS compatable side gears.

    Mike, I a'm running the DSS Level 5 axles that use a custom 33 spline outer stub shaft and hub. They are much stronger than stock. The stock Cobra axles use a 28 spline outer stub shaft that looks identicle to the MN12. I
    know the Cobra guys have had failures at the outer shafts also. So I would not say the stock Cobra axle is stronger at that area. See the two links these are cobra failures, looks real familar!!!!!!!!

    http://www.lx.net/jlynch/stub21.jpg

    http://www.lx.net/jlynch/stub6.jpg

    My point in my original post was that I've been running the Level 5 stuff for a couple months and have drag tested them and they will work in a MN12 car.


    Mike.......

  13. #28
    Join Date
    Jul 2003
    Location
    South Central Los Angeles
    Posts
    3,538
    im looking into replacing my axles, since i think its time, so are the mark viii's just a little better than the stock sc ones? thanks.

    ahhh nevermind it was a raxle vs stock sc
    Last edited by darkstar_one; 06-30-2006 at 04:05 PM.

  14. #29
    Join Date
    Mar 2006
    Location
    Chesterville, OH
    Posts
    197

    Talking Just some clarity

    So let me get this straight. I still ne to get my hands on a set of cobra axles for the inner CV. Everything else comes in the Kit? Pricey but I do plan on going over 700HP when alls said and done.

  15. #30
    Join Date
    Jul 2003
    Location
    Eastern (nee Western) PA
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    4,993
    Quote Originally Posted by Storm_Dragon
    So let me get this straight. I still ne to get my hands on a set of cobra axles for the inner CV. Everything else comes in the Kit? Pricey but I do plan on going over 700HP when alls said and done.
    At least no one can say you dream too small. Not that it's unreachable, just, wow, that's big.
    God bless!!!

    Former Birds:
    1990 SC auto ... red outside, gray cloth inside ... ~225,000 miles ... Sold.
    1990 SC auto ... white outside, gray cloth inside ... ~150,000 miles ... wrecked.
    1989 Base auto ... Crystal Blue metallic outside, dark blue inside ... ~160,000 miles ... Sold.

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