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Thread: LSD80% VS LSD40% M220 "Factory"

  1. #1

    LSD80% VS LSD40% M220 "Factory"

    I have not found information in relation to the Limited slip differential 220 80% in the 911 of 72. I have several questions
    1. In the '72 911S (oil side cover) was it an extra that was included in the original? I thought this until now but when I see the purpose sport I see that it is marked as an X. Indicating that it can be added. Until now I have thought that the limited differential slip on the 911s came from the factory ...
    2. Is there a document or vehicle record where the change from 40% to 80% in LSD can be noted? How was this change noted and when was it requested? When you asked for the extras, did you tell them that 220 did you want it at 80%? In that case, how was the distinction made?
    sorry for the capital letters! If an admin reads this and I can "normalize" the letter of the title I will be grateful

    Name:  1972principio.jpg
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    https://porschecarshistory.com/1972-...es-911s-914-6/
    Last edited by _gonbau; 06-09-2021 at 06:50 AM.

  2. #2
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    If I understand your question correctly, there was no progression on the Factory limited slip. Yes, they were available from the Factory but as options. Same with the distinction between 40 and 80% function. BTW, 80% is severe for a street car and these were usually ordered for competition. In this period you mention there were considerable variances on the transmissions including, ratios, ground vs machined gears, none-20%/-80% limited slip, and a gear driven external oil cooler. All these variables just on the trans! I hope this is helpful.

  3. #3
    Member #226 R Gruppe Life Member #147
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    FYI, I have rebuilt dozens of factory installed LSD’s in Mag gearboxes, 69-73, 911 and 914’s, all of them without exception were set at 80%. 40% wasn’t a common setting until circa the SC’s era. And non adjustable 40% around the Carrera’s and 964’s. There might be exceptions but not in my experience.

  4. #4
    To be clear to me. The '72 911 S's. They came from the factory with the LSD ... is this correct? I have to reread the documentation! But until now I thought so. So, were there different option numbers for a 40% LSD and another option number for 80%? Or when you asked for 911, you told the factory in what percentage you wanted it and if so. How did they differ when building them on the construction sheet? Did you target M220 even if it had a different%? Thank you both very much !!

  5. #5
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    I agree, the M220 was an option, never standard, and in the early cars was set for 80%. Even for the 73 911RS, it was an option and not always specified for the competition cars.
    Porsche Historian, contact for Kardex & CoA-type Reports
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    Researching Paint codes and Engine Build numbers

  6. #6
    I see that the 220 was optional and until today ... I had thought that the factory LSD came in the S ... I don't know why. Maybe I had confused it with the stabilizers ... Thank you very much and sorry for my stupidity. Apart from that, any details about whether the build sheet record is marked if the LSD is 80 or 40?

  7. #7
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    These cars continuing to be a learning experience. I've been on the driving and building side, but no experience tearing apart the gearboxes. My XREF is from a few early 911s with LSD. Again my personal experience [over 50 early 911s- yes I'm a big crazy and not a dealer] was very few with LSD and the only one with an 80% was an RS that had been raced in previous life and was still pretty much set up biased for the track. QUITE a surprise to hear that 80% was the common LSD, but ...again.. we keep learning. It also points out that even the Factory books don't always tell the real world tales.

  8. #8
    Member #226 R Gruppe Life Member #147
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    If the numbers aren’t rubbed off the bottom, factory installed LSD’s; 70-71 gearboxes would carry the suffix 10 (911/xx/10). 72-73 would carry the suffix 11 (915/xx/11). Later gearboxes were 12 and early chill cast Alu did not identify LSD’s

  9. #9
    with that we would have the number but if the LSD was in another percentage to the "normal" ... How would it be known? Observing the number can you observe the% and I do not know it? Or if you asked for the LSD "Touched" there was no way to differentiate it from a normal one? The explanations said here are appreciated and "FROM MY SHORT KNOWLEDGE" I also thought that LSD came to 40% originally and that 80% was something "unusual" ...

  10. #10
    Member #226 R Gruppe Life Member #147
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    Again all LSD’s in long hoods were 80%. If u wanted something different, u took the diff out and went into the service manuals, that outline the different locking values, and re-set it. Any numbers identifying LSD’s were only for that unit installed.

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