Clutch shaft and transfer gears, materials spec. anyone? | FerrariChat

Clutch shaft and transfer gears, materials spec. anyone?

Discussion in 'Technical Q&A' started by magnesium, Sep 20, 2018.

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  1. magnesium

    magnesium Karting

    Nov 15, 2003
    51
    #1 magnesium, Sep 20, 2018
    Does anyone know the material specification for the splined clutch shaft and (cast) transfer gears for a 1978 308 ? Also the hardening process and specification for the splines. I'm talking about part nos. #109400
    for the clutch shaft and #119721 for the top transfer gear.

    Thanks for any information on these.

    Matt.
     
  2. 335s

    335s Formula Junior

    Jan 17, 2007
    870
    SF Bay Area
    Full Name:
    T. Monma
    #2 335s, Sep 20, 2018
    This is heavy lifting, and I really do speak from experience...why not just get some spares from a breakers yard?
    They made 11-13,000 of these, so there is no shortage of them IMO, and the cost will be fractional to the manufacturing cost/cycle....

    FWIW: the gears: I personally would use a forged blank, and then get it ground on a Gleason 4000, 5 axis: IMHO, use 9310(hi nickel/molybdenum case hardening GOOD strength AND toughness properties and has HIGH hardenability with HIGH core hardness WITH high fatigue strength-"vac melt" is mo betta), hardened to Rc 60/62 after, then regrind to really dial in the specs for preload and backlash specs...this thing will fall out of bed and hold 19 millionths on the radius). I personally would advise ammonia gas ion nitriding, as opposed to carburizing due to depths and brittle issues post hardening-fwiw...but, remember: this process will give rise to a slight dimensional "swelling" of at most: 8 "tenths", thus the redressing post heat treating. As you are aware I'm sure, that 9310 machines nicely prior to heat treatment, therefore a minute surface "tune-up post heat treatment" is not only advise-able-but IMO: required....but this is just IMO....

    Splines are no doubt some sort of a broach DIN standard issue...that you'll be able to research fairly easily I suspect...

    shafts are pretty much either 52100(which has typically got a "sweet spot" for hardening at: yup-Rc 60/62...anything higher than this, and I'd opt for a different alloy), or 9310(these days it seems), which is becoming used everywhere it seems(e.g. almost ALL hub bearing assemblies in street cars these days use bearings made of 9310, or better...)
     
  3. magnesium

    magnesium Karting

    Nov 15, 2003
    51
    #3 magnesium, Sep 21, 2018
    Easier said than done. I've tried the usual sources but none has come up with anything useful. Rising prices over the last few years means that there just aren't as many cars being broken. Soon there'll be none. In fact these parts might even be available new but there are conflicts of information on what is actually being supplied and I have had experience of some pretty poor / unsuitable parts from the official channels. As everyone knows, they are supplying some reproduction parts that are truly awful quality (need I say water pumps for example!). I certainly haven't found the right shaft and gear combination off the shelf yet. Maybe I will but I'm not going to sit around waiting when I can explore all the options.

    The information you have given is helpful but I've got to come clean - I'm considering repairing these rather than remanufacturing which, as you said, is all doable but not spectacularly easy. I should emphasise the word "considering" because I'll only embark on it if I'm sure I can make a really nice repair. Don't dismiss the idea out of hand! Here is my logic:

    The only damage is to the splines other than that, the gear and shaft are perfect.
    If I knew the shaft material, I could weld, recut the splines and reharden (just the splines). This could be ground again after hardening and the shaft would be true. Not such a difficult repair and strength would be adequate. I'd specify a tighter fit on those splines too.
    The same could be done with the gear although that presents more difficulty in protecting the teeth hardness and in precision finishing the splines after hardening.
    Although it is acceptable to match a new gear with the old transfer gears (as long as it's the right type), I still think this is best avoided if possible. Well, that's a very slight advantage of repairing the existing gear.

    So what I really need is the material and hardening specs of the original parts.
    What hardness do you think the splines actually need to be?

    I'm considering other solutions too and continue to search for good parts whether used or new.
    Any further thoughts on this, the materials and other well-engineered repairs appreciated.
     
  4. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    25,138
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #4 Steve Magnusson, Sep 21, 2018
    Have you checked/discussed with Modena Engineering?:

    http://www.modenaengineering.com.au

    I don't recall seeing making helical spur gears in their manufacturing resume, but the 308 clutch shaft seems very much like the gearbox shafts that they are already making for TR/512TR (so "Ferrari" won't be completely Greek to them). Just a thought (and +1 to 335s comments about the "heavy lifting" -- not easy to make a gear with super-hard tooth surfaces that is also tough, and not brittle, elsewhere.)
     
  5. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
    34,091
    Austin TX
    Full Name:
    Brian Crall
    #5 Rifledriver, Sep 21, 2018
    I was recently made the exclusive US distributor for Modena Engineering components for Ferrari. Getting it made by Modena is no problem whatsoever, that being said it would be far easier, faster and less expensive to fix the splines and there are many in the US who do it well. That would be my advice. It isn't rocket science. There is one reason and one reason only the splines went bad.....the ring nut was left loose or was prevented from coming loose. Properly installed that splined connection is indestructible.
     
    vincent355 likes this.
  6. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
    34,091
    Austin TX
    Full Name:
    Brian Crall
    #6 Rifledriver, Sep 21, 2018
    FWIW the shaft shows available new. It was not a high demand item and fit a ton of cars. My bet is they are NOS, not repops.. The gear shows NLA.. I d call everyone. At one time Ferrparts had a mountain of misc new gears. It fit US and non US QV and Mondial QV.
     
  7. fatbillybob

    fatbillybob Two Time F1 World Champ
    Consultant Owner

    Aug 10, 2002
    26,407
    socal
    #7 fatbillybob, Sep 21, 2018
    RD,

    I don't see every post but where I travel on Fchat I have not seen a technical post from you in quite a while. I'm glad to see posts from you.
     
    tomberlin likes this.
  8. 335s

    335s Formula Junior

    Jan 17, 2007
    870
    SF Bay Area
    Full Name:
    T. Monma
    #8 335s, Sep 21, 2018
    Picture now MUCH clearer!

    I agree with RD completely-since the shafts ARE available, don't screw around with complex repairs which only tend to propagate error...
    I ALSO agree with the root cause of the ailment, now that the specifics of damage have been clarified...

    IMO-the radial slop which may exist, won't be a critical issue so long as proper axial torque is achieved.
    So long as said slop isn't "excessive"....If you get fixated on the splines in the gear being re-hardened-this is more involved than it appears. Since-in my memory-there is NO visual evidence of copper plating on these gears anywhere, one can reasonably conclude that ammonia nitriding gas/plasma-whatever-WASN'T used, as copper is what is used to keep the underlying area UN-hardened(your camshafts likely have residual copper "plating" on shaft areas BETWEEN lobes, so as to be able to straighten them AFTER heat treatment.) . Therefore normal conclusion would be carburizing. Good, cheap, fast, but shallow depth of hardness....
    You will be advised that AFTER dealing with the damaged splines-however you choose-the gear has to be annealed FIRST, then reworked, splines, THEN re-hardened. Again: starts to be "heavy lifting."
    Since I DO make rocket and missile parts on many an occasion, I assure you the process, while doable, is arduous and expensive...
    try new shaft first, since teeth are good, don't look for trouble....just focus on new ring nuts, Torrington bearings, and a good-accurate-torque wrench...
    good luck-be happy
     
  9. magnesium

    magnesium Karting

    Nov 15, 2003
    51
    #9 magnesium, Sep 25, 2018
    Those thoughts have been very helpful, thanks.

    And yes, although these splines are hard, unlike the splines on the clutch end of the shaft, they really don't need to be. There should be no force whatsoever on these splines if the assembly is tightened sufficiently.

    Fixing the slines does seem like a good option although I might now have found a clutch shaft at a good price too. I'd still prefer to keep the original transfer gear if possible but, if I do go the route of replacing it, can anyone tell me what the hand-written numbers on the transfer gears mean. Is this important to matching them? Mine are marked "01" but I have seen them with different and longer markings such as "0201".
     

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