Does the 246GT transaxle have any hypoid bevel gears? | FerrariChat

Does the 246GT transaxle have any hypoid bevel gears?

Discussion in 'Technical Q&A' started by Pantdino, Aug 30, 2015.

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  1. Pantdino

    Pantdino Formula 3

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    Jim
    #1 Pantdino, Aug 30, 2015
    The most recent Pantera club newsletter describes the ZF transaxle in the car as having spiral-bevel as opposed to hypoid bevel gears.

    The difference is that hypoid bevel gears have some sliding as part of their contact and thus need GL5 oils, whereas if there are no hypoid bevel gears you shouldn't need GL5 and can stick with GL4 oil, which is kinder to brass and aluminum.

    Does the 246GT transaxle have hypoid or spiral-bevel gears?

    Thank you,

    Jim Oddie
     
  2. Ferrari Tech

    Ferrari Tech Formula 3

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    #2 Ferrari Tech, Aug 31, 2015
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  3. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #3 Steve Magnusson, Aug 31, 2015
    Last edited: Aug 31, 2015
    Forgive me for going all technical ticky-tack, but a 246GT transaxle has neither hypoid nor spiral-bevel gears as Wade indicated. This is a spiral bevel gear set (the pinion axis and the ring gear axis intersect):

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    The gear set Wade posted (and what is used in a 246/308 transaxle and transfer gears) is a helical spur gear -- but the discussion still applies (helical spur gear or spiral bevel gear = no sliding = GL4 OK; hypoid bevel gear = some sliding = GL5 best).
     
  4. synchro

    synchro F1 Veteran

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    Scott
    #4 synchro, Sep 1, 2015
    If this Q is ending up asking for transaxle oil recommendations, there is only one; RedLine 75-90NS


    PS - after recently changing from Swepco 201, I no longer think these two oils are equal in a Dino transaxle
     
  5. finnerty

    finnerty F1 World Champ

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    #5 finnerty, Sep 1, 2015
    Last edited by a moderator: Sep 7, 2017
    There is a further distinction that differentiates a hypoid gearing from a spiral bevel gearing as well ---- The hypoid is a refined type of spiral bevel gear whose axis does not intersect with the axis of the meshing gear (in other words, there is an axial offset). The shape of a hypoid gear "tooth" is a revolved hyperboloid (that is, the pitch surface of the hypoid gear is a hyperbolic surface), whereas the shape of a spiral bevel gear surface is normally conical.

    Here is the configuration of a hypoid gearing --- it is readily identifiable at a lay-person's glance just by the relative 90 degree angles and the offset of the axes --- no other system has both characteristics.
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  6. Pantdino

    Pantdino Formula 3

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    #6 Pantdino, Sep 1, 2015
    I have been using RedLine 75-90NS in the Dino and Pantera, but it is a GL 5 oil

    Why wouldn't RedLine MT 90, which is a 75W-90 GL 4, be a better choice if GL 5s are inherently bad for softer metals?
     
  7. GordonC

    GordonC F1 Rookie
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    #7 GordonC, Sep 1, 2015
    Redline MTL or MT90 is the transmission oil recommended by Brian Crall, aka Rifledriver.

    I switched to MTL (75W80 GL4) this spring from Redline 75W90NS GL5 in my 308 GTS QV, and the MTL made a significant improvement with shifting to second gear when cold.
     
  8. Pantdino

    Pantdino Formula 3

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    #8 Pantdino, Sep 3, 2015
    That's what one would expect based on the viscosity at cold temps. These trannys are stiff when cold bec the oil is thicker when cold. After it warms up it is thinner and hence the car shifts better.

    I suppose if you tracked your car or drove the snot out of it for long periods you might want the thicker oil in there, but for most of us the MTL is probably a better choice. I think I'll change.
     

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