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Thread: Gear Oil...

  1. #1

    Gear Oil...

    Hello Guys,

    What grade gear oil should be used? Mine car is a '67S and will I need GL-4 oil or will GL-5 do fine. I've read that GL-5 contains 50% more sulphur and it tends to etch the synchros, causing them to wear prematurely....

    Also is there any good using a LSD oil in a non-LSD tranny? Some have told me that the LSD properties is good to help the synchros....

    So, GL-4 or GL-5? My VW calls for GL-4. How about the early 901 box?

    Thanks!

    Sprint.

  2. #2
    Goldmember ttweed's Avatar
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    Sprint-
    There is a lot of debate about this and no real consensus about what is best. The difference is in the friction modifiers used in oils for LSD clutches. They are not recommended for non-LSD trannys, only for ZF LSD types, to keep the clutches from chattering. See this link at Paragon Products.
    I use Swepco in my non-LSD 901 and Mobil synthetic gear lube in my LSD-equipped 915 (which has a Torsen type LSD.)

    TT
    Tom Tweed
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  3. #3
    Moderator Chuck Miller's Avatar
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    This is how it worked out for me in my old 'crunchy' (soon to be rebuilt) 915/LDS gear box…

    Always put Swepco + LSD additive until about 2 years ago when I tried the highly recommended Torco synthetic.

    ..."put this stuff in your old tired boxes and they'll be like new"

    Again, this WAS an old tired box, and the synthetic was TERRIBLE ! … even with a LSD additive it was hard shifting plus ALLOT of diff. chatter.

    I immediately switched back to Swepco + the Kendall LDS additive and all was well again.

    An old Porsche mechanic said that with the 'old' 901 and 915 gear boxes the new synthetics were TOO slippery and the syncros needed a slight bit of resistance to work properly…

    ... go figure

    My two cents,
    Chuck Miller
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  4. #4
    And..I've been running TORCO synthetic in my 915 with factory limited slip, and love it. Gordon ledbetter "freshened" my gearbox a few years ago...to as new. 75-140 TORCO, GL6 with limited slip additive. So, I'd say choice of gear oil may depend a lot on the condition of the gearbox? One plus here...it doesn't cost an arm & a leg, materials wise, to try various products until you find the one that works well for you.
    Paul D. Early S Registry #8 - Cyclops Minister of West Coast Affairs
    "Now, to put a water-cooled engine in the rear and to have the radiator in the front, that's not very intelligent." -Ferry Porsche (PANO, Oct. 1973)

  5. #5
    Originally posted by ttweed
    Sprint-
    There is a lot of debate about this and no real consensus about what is best. The difference is in the friction modifiers used in oils for LSD clutches. They are not recommended for non-LSD trannys to keep the clutches from chattering. See this link at Paragon Products.
    I use Swepco in my non-LSD 901 and Mobil synthetic gear lube in my LSD-equipped 915.

    TT
    Ok, the link says not to use FM in non-LSD cars, so that throws the theory my old mech (whom I've also thrown out the window) has that LSD oil is good for all trannies...

    He said something about his own 3.2 Carrera being 'locked' in 5th gear when he coasts to the lights and can't get it free (very difficult) till he put LSD oil inside and things got better... Makes any sense?

    My car is getting like that too... If I hold 4th gear for too long, it's hard to get into 5th. Not that I can't find the gear but it seems harder to slot it in?

    And after a long highway drive in 5th, I find some difficulty to go to neutral...

    Any thoughts?

    Thanks!

    Sprint.

  6. #6
    Originally posted by Chuck Miller
    This is how it worked out for me in my old 'crunchy' (soon to be rebuilt) 915/LDS gear box…

    Always put Swepco + LSD additive until about 2 years ago when I tried the highly recommended Torco synthetic.

    ..."put this stuff in your old tired boxes and they'll be like new"

    Again, this WAS an old tired box, and the synthetic was TERRIBLE ! … even with a LSD additive it was hard shifting plus ALLOT of diff. chatter.

    I immediately switched back to Swepco + the Kendall LDS additive and all was well again.

    An old Porsche mechanic said that with the 'old' 901 and 915 gear boxes the new synthetics were TOO slippery and the syncros needed a slight bit of resistance to work properly…

    ... go figure

    My two cents,
    I'm thinking of trying Royal Purple's tranny oil. Anyone tried it before?

    I'm in Singapore. Can't find any Swepco here...

    Sprint.

  7. #7
    Originally posted by pwd72s
    And..I've been running TORCO synthetic in my 915 with factory limited slip, and love it. Gordon ledbetter "freshened" my gearbox a few years ago...to as new. 75-140 TORCO, GL6 with limited slip additive. So, I'd say choice of gear oil may depend a lot on the condition of the gearbox? One plus here...it doesn't cost an arm & a leg, materials wise, to try various products until you find the one that works well for you.
    Sigh... Alas, I'm in Singapore. Too far away with too few good products.

    Sprint.

  8. #8
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    A gear oil with friction modifier will work OK in a car without limited slip but it won't work as well as a gear oil without friction modifier. A transaxle design is unique in that the diff and gear box share the same oil. Normally a diffferential would want something very slippery and the synchro gear box would want something not too slippery for easy synchro engagement. Major shifting problems are likely an adjustment or synchro issue.
    Jason Burkett
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  9. #9
    Originally posted by Paragon
    A gear oil with friction modifier will work OK in a car without limited slip but it won't work as well as a gear oil without friction modifier. A transaxle design is unique in that the diff and gear box share the same oil. Normally a diffferential would want something very slippery and the synchro gear box would want something not too slippery for easy synchro engagement. Major shifting problems are likely an adjustment or synchro issue.
    Thanks Jason! Does it matter what kind of limited slip the tranny has? I think only the clutch type makes that clatter, right? So if we use a torque biasing one like GT or Quaiffe, we won't need LSD oil?

    Sprint.

  10. #10
    Sprint? I've heard nothing but good about royal purple products. I've never tried them personally. Perhaps you'd be willing to be our guinea pig?
    Paul D. Early S Registry #8 - Cyclops Minister of West Coast Affairs
    "Now, to put a water-cooled engine in the rear and to have the radiator in the front, that's not very intelligent." -Ferry Porsche (PANO, Oct. 1973)

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