Boxer differential failure | FerrariChat

Boxer differential failure

Discussion in 'Boxers/TR/M' started by nelson, Jan 31, 2025.

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  1. nelson

    nelson Rookie

    Mar 10, 2011
    19
    CT
    Full Name:
    Nelson Heumann
    I was accelerating onto the highway, heard a clunk, and then saw black smoke billowing from the rear of my Boxer. After I stopped, I could see oil dripping from the tranny where the left driveshaft connects. When I took the transmission apart, I could see the left flange that carries the left differential bearing, had cracked, see picture. The differential had also cracked apart where it was welded together, see picture. Because of the cracked parts, getting the broken differential out took quite some time, as the quill shaft had been pinched by the broken flange and wouldn't move.
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  2. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    26,598
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    Situation normal -- the weld in the diff carrier breaks and then the irregular angled surfaces move against each other "ramping" apart = breaks the structure holding the bearing outer race.
     
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  3. ago car nut

    ago car nut F1 Veteran
    Silver Subscribed

    Aug 29, 2008
    5,473
    Madison Ohio
    Full Name:
    David A.
    It happens, that is why many have replaced welded diffs.
     
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  4. dontilgon

    dontilgon Formula Junior

    May 30, 2011
    332
    NY/PA
    Full Name:
    Joseph
    What year and mileage ?
     
  5. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
    9,418
    southwest Germany, France ( Alsace ) and Thailand
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    romano schwabel
    this is more typical for TR´s.
    as I always say: the question is not if it will break, only when
    but sorry to see this
    what about the crwon gear? also damaged a little? on the photos still look ok
     
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  6. TestaDDS

    TestaDDS Karting

    Sep 6, 2015
    81
    France
    Full Name:
    RM
    Sorry for what just happened to you, Nelson.
    Glad I preemptively changed the differential on my Testarossa 3 months ago.
     
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  7. Spitfire

    Spitfire Formula 3

    Nov 16, 2006
    1,602
    You could reach out to Newman and see if he has a billet diff that might work for you.
     
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  8. 2dinos

    2dinos F1 Rookie

    Jan 13, 2007
    2,973
    A known problem with no way to predict when it will happen. Like earthquakes.

    Hopefully the repair process goes smoothly. GT Car Parts has the side covers machined from billet.
     
  9. bjunc

    bjunc Formula Junior

    Jun 18, 2023
    412
    Miami, FL
    Full Name:
    Robert
    Nelson, you seem to be handling this a lot better than I would.

    Surprised this happened on a Boxer. I'd be very curious to know what mileage the car had. Or maybe what tires were on the rear. I thought this was more prone to happen on the more powerful cars (TR).
     
  10. samsaprunoff

    samsaprunoff F1 Rookie
    Silver Subscribed

    Jun 8, 2004
    4,414
    Edmonton, AB Canada
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    Sam Saprunoff
    Good day Robert,

    Given the past threads on here, a number of Boxers also suffered a similar fate... and so it is not uncommon at all.

    Cheers,

    Sam
     
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  11. nelson

    nelson Rookie

    Mar 10, 2011
    19
    CT
    Full Name:
    Nelson Heumann
    My car is an '84 with about 75k miles. The crown gear was fine.
     

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  12. nelson

    nelson Rookie

    Mar 10, 2011
    19
    CT
    Full Name:
    Nelson Heumann
  13. nelson

    nelson Rookie

    Mar 10, 2011
    19
    CT
    Full Name:
    Nelson Heumann
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  14. nelson

    nelson Rookie

    Mar 10, 2011
    19
    CT
    Full Name:
    Nelson Heumann
    the transmission had been rebuilt in the early 2000s, so I assumed the differential had been replaced then. Silly me.
     
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  15. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
    9,418
    southwest Germany, France ( Alsace ) and Thailand
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    romano schwabel
    you are very lucky :)

    re-shim is normal to get the right result

    where you got an other cover from?
     
  16. 2dinos

    2dinos F1 Rookie

    Jan 13, 2007
    2,973
    I second Sam ....+1

    There are many stories on F-chat of "cream-puff" / lo-miles Boxers of all variants that the weld gives out and causes surprisingly light damage (like just the carrier, and somehow everything else was fine), to OMG / sick feeling for the parts hunt for precious, rare, and very expensive hardware needed to sort out. The connection to the failure and resulting damage is not necessarily a direct correlation. Some bad events occurred at low speeds etc.

    I couldn't stand it knowing, or rather not-knowing I might just take the car out on a beautiful day for a coffee etc, and have this thing break. I replaced it and now feel much better about taking her out.

    Maybe others can chime in as to predictive things linked to the failure like car was built on Tuesday etc ?? I just don't know and gathering that data is unlikely at best.

    BTW: Is that a hockey puck holding the diff in position for the photo? Awesome !
     
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  17. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
    36,819
    Cowboy Capitol of the World
    Full Name:
    Brian Crall
    Two lines on a graph. One is how well welded that specific carrier was. The other line is the totality of high stress events in the life of the carrier. One is always an unknown. The other is in all but a very few cases an unknown.

    Good luck predicting failure.
     
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