Limited slip differentials on vintage F cars | FerrariChat

Limited slip differentials on vintage F cars

Discussion in 'Vintage (thru 365 GTC4)' started by Horsefly, Dec 13, 2005.

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  1. Horsefly

    Horsefly F1 Veteran

    May 14, 2002
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    Starting in the late 1950s, Chevrolet had their limited slip differentials called "posi trac". Ford, Dodge and others had their brand names of the same thing. If one wheel was spinning, power was transferred to the other wheel. Pardon my ignorance, but did Ferrari have a similar system or were their older differentials simple single tracks. Did they have a version of a limited slip differential? If so, what years and what models were they used in?
     
  2. jsa330

    jsa330 F1 Veteran
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    I'm pretty sure my 330 has "positraction"...it leaves two rubber stripes when the rear wheels spin.:)

    It has all the 60's muscle car stuff...3 deuces, tuned headers and dual exhaust, 4 speed trans, positraction, puts out 1.2 horsepower per cubic inch.

    I know that's not much of an answer...I can only guess that it was a standard feature.
     
  3. boxer frank

    boxer frank Karting

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    alot of models have clutch type zf lsd
     
  4. Bryanp

    Bryanp F1 Rookie

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    #4 Bryanp, Dec 13, 2005
    Last edited by a moderator: Sep 7, 2017
    Ferrari used the ZF limited slip differential long before Chevy - Ford etc. Here is one with the matching outer case removed - from a series II 500 Mondial.
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  5. Bertocchi

    Bertocchi Formula 3
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    This type is commonly reffered to as "cam and paw". I found this type in factory TR racing cars.
     
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  6. Rifledriver

    Rifledriver Three Time F1 World Champ

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    Cam and pawl, also known as Chicklets.
     
  7. Rifledriver

    Rifledriver Three Time F1 World Champ

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    While the early race cars had the cam and pawl differentials from the 275s and up pretty much everything has the clutch type positraction differentials. Up until recent years with E diff cars which are basically mini auto trans clutches.

    I am sure there are exceptions which Dyke can comment on.
     
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  8. DWR46

    DWR46 Formula 3
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    This is going back in this thread, however, the original ZF limited-slip unit is totally different in concept from the later American clutch type limited-slip differentials.
     
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  9. DWR46

    DWR46 Formula 3
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    Brian: Early 275's used the cam and pawl units. At roughly the introduction of the Long Nose cars, the factory began to use "clutch" type LSD's. All 330 GTC and later cars used Clutch Type units. The ZF cam and pawl unit does NOT need LSD additive in the gear oil. No clutches, no additive needed.
     
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  10. TTR

    TTR F1 Veteran
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    I'm not sure what you mean by "later", but I've always considered 1957 and up Chrysler "Sure-Grip" being quite similar concept to ZF limited slip setups I've encountered in Daytona transaxles.
    Or perhaps I'm not looking at or understanding them correctly ?
     
  11. Rifledriver

    Rifledriver Three Time F1 World Champ

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    You are thinking of the ZF clutch type. Not the ZF cam and pawl type.
     
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  12. DWR46

    DWR46 Formula 3
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    Timo: Daytona's use clutch type LSD's, similar to the GM, Chrysler and Ford units.

    ZF developed the Cam and Pawl style LSD around 1935 for use in the Mercedes-Benz Gran Prix cars. Most Italian and German performance cars of the 1937-65 era used this style LSD. It was amazing for its time, but is not actually a very good way to limit slip. As Brian stated, the "chicklets" do only a fair job of locking the axles together and they are a high wear item. We replace them consistently in the Maserati race car transaxles. Luckily, Crosthwaite & Gardiner can supply them today.

    ZF went to the "American" style LSD, as I stated, in about 1966 and this is what is used on the late 275, 330 GTC, Daytona, Boxer, etc.

    While the "American" style unit is superior to the original 1935 ZF design, it also has its limits, as if you want aggressive locking action, as in racing, clutch life is not very long, and the units can "ratchet" and "clunk" when the car slowly turns sharp corners. Modern additives can minimize the "clunking" but they also reduce the effectiveness of the limited slip action.

    Finally, for American cars, the old Detroit Locker style is extremely effective and durable, but very "clunky" and "crude" in action. 1965 Shelby GT350's used them and the next year they went to the standard American clutch style as owners thought they had destroyed the entre rear axle when they turned a slow, tight corner.

    Enough of this, hopefully my ramblings have made some sense.
     
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  13. NYC Fred

    NYC Fred F1 World Champ
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    Sorry. Had to...

     
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  14. TTR

    TTR F1 Veteran
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    #14 TTR, Sep 3, 2024
    Last edited: Sep 3, 2024
    Brian & Dyke,
    I wasn't aware of ZF's history with these and my ZF differential/LSD (<- that just seems/sounds weird) experience is only with transaxles found in Daytonas and alike, but thanks to Dyke's brief summary I learned something today. :)
    And yes, I've heard of Detroit Locker, but never serviced or worked on one.
    There was another type used among some hot rodders when & where I grew up, but that involved some welding ... :D
    ... and they didn't seem to last very long nor offered any limited slippage. :rolleyes:
     
  15. Rifledriver

    Rifledriver Three Time F1 World Champ

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    #15 Rifledriver, Sep 3, 2024
    Last edited: Sep 3, 2024
    Thanks to Dyke I did too. Was not aware of the origin of the cam and pawl type but it makes perfect sense. Coming off turn 1 at Avus they needed both tires driving.
     
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  16. JCR

    JCR F1 World Champ
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    The Detroit Locker was offered as part of the "Drag Pack" option on the Ford 9 inch rear on select muscle cars.
     
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  17. Admiral Goodwrench

    Admiral Goodwrench Formula Junior

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    Dyke,

    Appreciate your early history lesson. All I have to offer is this shot of a chicklet, only the end views show in post #4.

    Best regards,

    Robert


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  18. Rifledriver

    Rifledriver Three Time F1 World Champ

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    Was not aware of that. Have rebuilt a number of 275 transaxles including long nose comps and never ran into one.
     
  19. Bertocchi

    Bertocchi Formula 3
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    I am in the midst of rebuilding a 275 GTB/4 transaxle that suffered some minor damage to the LSD. As many of the experienced people here know the ZF Clutch type differential has many adjustments to regulate the amount of lock up or breakaway torque.
    The main method is adjust the stack height of the clutch pack with clutch discs of varying thicknesses. These were not easy to find but were at one point routinely available. I have actually reproduced some thicknesses.
    ZF engineers were clever and racers that still use this set up won't use anything else, many going as far as installing shims to the clutch pack to achieve the exact amount of lock up desired.
    The breakaway torque is of course related the engine torque so different dispalcement engine will require a different clutch pack to achieve the same result. Unfortunately the only clutch discs available from Ferrari parts vendors are 2mm.
     
  20. mechaniker

    mechaniker Formula Junior
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    You can ask limitedslip.de the guy knows everything about ZF Diffs. He has a ton of parts available. He also suggests diff settings for specific cars and needs.

    i only mention him, as i‘m a very happy customer. He gets money from me, not the other way around.
     
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  21. turbo-joe

    turbo-joe F1 Veteran

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    W O W ! ! !
    a very informative side. thank you for posting, never heard before
     
  22. Bertocchi

    Bertocchi Formula 3
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    The site appears to be entirely in German. Does he speak English?
     
  23. mechaniker

    mechaniker Formula Junior
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    Hi David

    I think so. If not, drop me a PM and I can translate.
     
  24. swift53

    swift53 F1 Veteran
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    If you right click, it will allow you to translate. Took me awhile, but well worth it.
    Regards,
    Alberto

     
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