supposedly an LSD, but computer says no

Discussion in 'Parts' started by eriknetherlands, Jul 17, 2017 at 6:29 AM.

  1. eriknetherlands

    eriknetherlands Active Member

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    Hi,

    Looking for collective wisdom here.

    Locally i found a supplier offering an e9 differantial and he is claiming it to be an LSD. However from my knowledge, if it is an LSD it should have the letter "S" stamped right above the ratio (11:38< perfect for my 3.0 CS).

    It doesn't have the "S".
    Is it / can it be then an LSD?
    see images.

    by the way, as i currently (still) have an automatic gearbox, does the installation of an LSD now make any sense, or is that only interesting when doing a 5sp swap?

    If it is an LSD, im inclinded to part-hoard it just to see what i can do with it...
    Erik.
     

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  2. Mike Goble

    Mike Goble Active Member

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    Is it possible to put an LSD carrier into a case that came with an open carrier?
     
  3. Stevehose

    Stevehose Well-Known Member Site Donor $

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    the S is painted, not engraved so it could have come off and I believe the cases are identical.
     
  4. eriknetherlands

    eriknetherlands Active Member

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    Steve,

    Reference I have are these images, posted earlier here as being true LSD's. They have the "S" stamped in there, right above the ratio.
    So as my local parts guy has somethign that is different, what is it?

    @ Mike, Yes I think is possible to swap the internals as the housings are identical, otherwise identification wouldn't be such a pain.
    Question then is; how can one identify an LSD based on function, when on a workbench? unscrewing the vent cap and looking in?
     

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  5. Ohmess

    Ohmess I wanna DRIVE! Site Donor $

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    Unscrew the vent cap is foolproof. If you see the lsd carrier when you unscrew the vent cap, then you have an lsd.

    Alternatively, you can place your hands on the output flanges and turn one whilst feeling the other. If the non-driven flange turns in the same direction, you have an lsd. If not, no joy.
     
  6. Wladek

    Wladek Active Member

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    This is how LSD inside case look like thru vent cap. But you should also read what is stamped on that case for example "4061006110 195683 S25" or S0, or S40" - S.. mean lock % (S25 - 25% lock, S40 - 40% lock etc.)
    It doesn't metter if you have 5-speed or 4-speed gearbox - LSD is better for better control feel in sporty driving RWD cars. Very shortly - LSD make both rear wheels rotate when for example one of them have better grip and the other have worse grip. When one wheel have worse grip in NON-LSD, diff will put all power on that wheel, and the wheel with good grip will not receive power at all.
    For example with LSD is much easier to drift. Probably all race cars have LSD.
    For inexperienced drivers or just for normal city driving / slow driving non-LSD will be probably better choice, safer.
     

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    Last edited: Jul 17, 2017 at 10:11 AM
    Ohmess, eriknetherlands and sfdon like this.
  7. HB Chris

    HB Chris Well-Known Member Site Donor

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    My LSDs have a stamped S.
     
  8. Markos

    Markos Parts Hoarder Site Donor $

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    A pic of my stamp. Lots of dirt and oil but visible. It is on the passenger side rearward of the axle flange:


    [​IMG]
     
  9. Tony.dreamer

    Tony.dreamer Member Site Donor

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    Does anyone know what year BMW start offering LSD on thier E9 coupe?
    I was told it was an option... but I have not come across anything that indicates when ?
     
  10. HB Chris

    HB Chris Well-Known Member Site Donor

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    From the start I believe
     
  11. Wladek

    Wladek Active Member

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    I think with starting of production 2800cs so 1968. LSD was mostly mounted with automatic gearbox.
     
  12. Tony.dreamer

    Tony.dreamer Member Site Donor

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    IMG_1638.JPG IMG_1639.JPG IMG_1641.JPG IMG_1642.JPG IMG_1643.JPG IMG_1644.JPG IMG_1638.JPG IMG_1639.JPG
    Ok, I am a bit confused! Somewhere I read that the LSD has a painted large "S" on the case and here it was mentioned that "S" was actually stamped on the case ...
    I have two identical differential case with identical casting numbers next to each other in the following pictures:
    1- the oily and dirty one has a "white " large "S" painted on it and it has 11 38 stamped on the case. This one I purchased recently from a reputable BMW parts reseller as a "bolt in LSD " for my E9.
    2- the clean bead blasted( but now rusty) one came out of my 1971 2800 CS that I am restoring. It also has 11 38 stamped on the casing. But also it has "S" stamped on .
    Inside of both look identical to each other and the same as the photo earlier by Wladek .

    Can you folks shed some light on this please ? Do I have two LSD?

    Cheers!
    Tony P.
     
    Last edited: Jul 18, 2017 at 10:52 PM
  13. Wladek

    Wladek Active Member

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    Just painted "S" might mean that diff was originally rebuild from open to LSD by BMW, diff might also have painted "E" (ersatz teil).
     
  14. Tony.dreamer

    Tony.dreamer Member Site Donor

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    So the "S" stamped on the case was actually made as SLD originally ..... so I do have two LSD's. ..
     
  15. eriknetherlands

    eriknetherlands Active Member

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    IF it turns out you do have 2 LSD's, just feel christmass comes early this year!

    Based on the comments & images above, i think you do have 2 LSD's.
    For reference a picture of my diff, which is clearly different:
    - In all (believed) LSD's pictured above, when photographed through the vent hole, the carrier can be seen. All LSD diffs in the pic above show a slot in the circle that is on the internals (carrier) of the diff. In my non LSD diff this circle element has no slot, it looks like a solid round bar. In my Non LSD diff, the end of this round bar lies flush with the carrier outer surface, in the LSD's that plane appears to be curved, lying below the level of the outside of the carrier.
    - The LSD's pictured above also do not have a groove around the internal element. My Non-LSD does have this groove, all around.

    See pic for clarification,
    (Sorry for the dark image of the Non LSD. I never photographed with this purpose in mind)

    Is this a definite tell tale then?
     

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  16. Gransin

    Gransin Active Member Site Donor

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    Not according to this thread, there seems to be 0% LSDs that actually isn't a LSD even thou it looks exactly like one.

    http://www.e9coupe.com/forum/threads/inside-a-lsd-0-diff.24885/
     
  17. Gary Knox

    Gary Knox Active Member Site Donor

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    Erik,

    Can't you just rotate the output flange on one side of the diff in either direction - if the opposite flange rotates that same direction, it's a LS. If it rotates the opposite direction, it's an open differential.
     
  18. Wladek

    Wladek Active Member

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    It will be better if he look thru vent hole & read what is written on lsd case inside - because even lsd case inside might be for example 0% lock and both sides will be rotating at the same direction, but it will be still lsd technically similar to open one.
     
  19. Ohmess

    Ohmess I wanna DRIVE! Site Donor $

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    That 0% lock makes no sense to me. Did you ever figure out why in the world BMW would make such a thing?
     
  20. Wladek

    Wladek Active Member

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    The only answer that make sense to me is that BMW at some production years had to much LSD cases, or haven't typical Open type cases at that particular moment of production.
     

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