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Hypoid-What does it mean?

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  • Hypoid-What does it mean?

    I told the fellow at the auto parts store that I needed hypoid lubricant for the differential of my car. He showed me a plastic bottle of Castrol HYPOY C Gear Oil SAE 80W-90. He told me that this was the same as hypoid lubricant because hypo meant high pressure. I didn't try to tell him anything about hypoid gears because I was not sure I could explain it to him, as I was not positive that I knew enough to do so.

    Now, I have some questions:
    1. Can we assume that the HYPOY is in reference to hypoid?
    2. What does the "C" mean?
    3. It is stated on the bottle that it provides excellent performance in manual transmissions and differentials but with the hype about the need for different lubricants in old cars than in current cars, I am still not sure if this will be safe for my 1950 Champion?

    I Googled the word hypoid and the following is one bit of information a fellow has written. Are his comments accurate?

    Copied from his site:
    > The book is telling me to use Non-Hypoid gear oil 80W or
    >80W/90 on the manual transmission and GL-5 hypoid gear oil 90W on
    >the rear axle.

    A manual transmission won't usually contain hypoid gears, so it
    doesn't need an EP oil. Rare exceptions are those transaxles where the
    crownwheel and gearbox share the same lubricant. Although an EP oil is
    more complex to manufacture, it has no disadvantages when used in
    instances where the EP attribute isn't strictly required. Manual
    steering boxes and other slow-moving oil-containing components are
    often filled with 90 weight oil. It's usual to buy EP90 because that's
    what the axle requires, then use the same oil for all other
    components.

    There's little practical difference between 80 & 90 weights. I fill
    everything with EP80 and I've never had a problem.

    There's an increasing trend amongst manufacturers to reduce the number
    of different lubricant types required. My own gearbox (5 speed Range
    Rover) runs on ATF, but 20W/50 engine oil or EP90 axle oil are equally
    permissible.

    --
    Andy Dingley




    Jimmie
    Orange County, Indiana
    1950 CHAMPION -ORANGE COUNTY, INDIANA
    sigpicJimmie
    Orange County, Indiana
    1950 CHAMPION -ORANGE COUNTY, INDIANA

  • #2
    Andy-

    My comments here are a summary of many posts on the Rolls-Royce Owners' Club website. The usual disclaimer applies - user of advice beware! I believe I am correct, but of course can be wrong.

    A hypoid rear axle has the driveshaft centerline passing below the axle centerline. The original purpose was to eliminate the driveshaft tunnel in the rear seat. The pinion teeth contact the ring gear teeth at a point, which mushes out into an ellipse under load. Contact pressures are very high, so EP (extra pressure) additives are needed to avoid scoring. Hypoid oil MUST be used in hypoid gear sets, or you wind up with a pile of metal shavings in the bottom of the gear case.

    A spiral bevel rear axle has the driveshaft centerline intersecting the axle centerline. The pinion teeth contact the ring gear teeth on a line. Contact pressures are much lower, so EP additives are not needed. Many pre-WWII cars have spiral bevel gear sets.

    The early EP additives (40s and 50s) were incompatible with each other (oil brands could not be mixed) and further tended to attack yellow metals (brass and bronze, often used in spiral bevel gear sets). Modern EP oils do not attack yellow metal, and generally can be safely used even in the older spiral bevel gear sets that have brass and bronze internal parts.

    So, spiral bevel gear sets MAY use modern EP oils.

    Almost all modern rear axles are hypoid, and you MUST use EP oil.

    If the axle is a locker or limited slip, there are additional requirements. See the car manufacturer's specs. If you are the rare bird with a spiral bevel gear set (and the newest I know of is in the 1953-54 Austin Healey 100-4 BN1) and are anal retentive, the only non-EP oil I know of is made by Penrite, an Australian firm. It costs! Thus, it is difficult to buy any gear oil that is not EP.

    The SAE 85-90, 90-140 etc oils sold in Parts-R-Us for use in rear axles are all EP. You should find this somewhere on the label. So, relax and enjoy life!

    Best, Phil.

    Philip W Birkeland
    1950 Studebaker 2R10

    Comment


    • #3
      Most older manual transmissions call for 50 motor oil, even large truck transmissions. Gear oil in most transmissions due no harm but can make them a little stiffer to shift especially when cold. Some later transmissions call for ATF and use of gear oil in some models(ZF 5sp comes to mind)will cause gear grinding when you shift. The ZF use steel blocking rings and don't work well with gear oil for some reason.

      Comment


      • #4
        Without referring to books (which are at home, and I am not)

        Old transmissions and differentials that have some brass or bronze parts in them usually do [u]not</u> get EP gear lube.
        IIRC, there is some Boron (or is it Borax?) in EP oil that can corrode the brass/bronze.
        That's why they use a straight weight motor oil in there instead.
        HTIH
        Jeff[8D]
        HTIH (Hope The Info Helps)

        Jeff


        Get your facts first, and then you can distort them as much as you please. Mark Twain



        Note: SDC# 070190 (and earlier...)

        Comment


        • #5
          The term "hypoid" actually refers to the geometric shape of the gear teeth in the rear axle. You will note that the axis of the pinion shaft passes well below the axis of crown gear (and of the axles, of course).

          Because of this, there is some unavoidable sliding contact between the gear teeth, instead of a strictly rolling contact as found in transmission gears. Hence an EP-rated gear oil is required. Since the EP-rated oils were developed for use in hypoid-gear axles, it follows that some derivative of the name shows up in the oil branding.

          Gord Richmond, within Weasel range of the Alberta Badlands
          Gord Richmond, within Weasel range of the Alberta Badlands

          Comment


          • #6
            I don't know if modern GL-5 EP gear lube still attacks bronze/brass parts but I helped my dad rebuild his 1970-ish Gravely (Studebaker!) tractor. He had always run EP gear lube in the gearbox which uses a very large bronze worm gear. When we pulled that apart it looked pitted and almost porous in spots. We found a new gear, replaced every seal and bearing, then found a source for the recommended GL-4 90W that he should have been using all along. Damage was done, but it did take 35 years to cause a problem and of course much of that time was with older gear lube.

            Nathan

            _______________
            _______________
            http://stude.vonadatech.com
            https://jeepster.vonadatech.com

            Comment


            • #7
              Hyphoid gears have curved teeth. These teeth slide together as they mesh, resulting in a larger contact area and less noise in forward revolution, but require a lubricant that protects the teeth surfaces during the sliding process.

              Comment


              • #8
                That sounds almost personal[}][:0]

                quote:Originally posted by buddymander

                Hyphoid gears have curved teeth. These teeth slide together as they mesh, resulting in a larger contact area and less noise in forward revolution, but require a lubricant that protects the teeth surfaces during the sliding process.
                HTIH (Hope The Info Helps)

                Jeff


                Get your facts first, and then you can distort them as much as you please. Mark Twain



                Note: SDC# 070190 (and earlier...)

                Comment


                • #9
                  That's what SHE said...

                  Comment


                  • #10
                    Most Studebaker manual transmissions except for four speeds use either SAE 40 engine oil or SAE 90 GL-1 gear oil which I prefer. NAPA has SAE 90 GL-1 gear oil but most stores don't have it on the shelf. My local NAPA store gets it out of the warehouse for me when I need it. Use a GL-5 gear oil in differentials as they require an extreme pressure lube. I would recommend 80W-90 for most applications unless you're living in a hot climate or use your car for towing, then 85W-140 would be a better choice. Castrol Hypoy C is a GL-5 oil so you can use in your differential, but not in your transmission. Bud

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