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Thread: 1975 R90/6 Funky rear shaft housing oil color

  1. #1
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    Question 1975 R90/6 Funky rear shaft housing oil color

    Yesterday, I changed the engine, transmission and drive train fluids (engine oil, transmission, and rear shaft housing, final rear drive). The transmission and rear shaft and front shaft drive all require the same weight of oil, 80W-90 hypoid gear oil. The surprise came when I emptied the rear shaft housing oil. It was a milky yellow color. The transmission and the rear drive looked like what I expected, golden yellow. This is the second time this has happened. Can someone explain why the rear shaft housing oil looks so different from the transmission and the rear drive oil? Thanks.

  2. #2
    Registered User ebeeby's Avatar
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    Sounds like water is getting in it and what you are seeing is that emulsion.

  3. #3
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    Usually any gear oil drain that looks "milky" is due to water contamination - the water and oil do not quite mix and form an emulsion something like latex paint
    which coats the surfaces in the shaft - it may take a couple of changes to get all this cleaned out - find the source of the water entering the shaft

  4. #4
    Monza Blue 1974 R90/6
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    The source of the leak has to be the boot between the transmission and the swing arm/drive shaft housing, right? Where else could water get into the drive shaft on a /6? Was it washed with a pressure washer?

    Good news is it only takes a little oil (150 cc's?). So you can change it one a week or so for the next couple of weeks to see if it is improving; or, continues to get contaminated.

    Barron

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    Same old thing

    I just drained the oil again after riding for less than 50 miles and have the same problem. The oil is milky brown and I have not washed the bike nor has it been driven in the rain. I will flush it out overnight and refill with 80W-90 oil. Maybe it will take a few times, but why?

  6. #6
    Administrator 20774's Avatar
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    Condensation?? Where do you live?
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  7. #7
    #4869 DennisDarrow's Avatar
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    Perhaps it is time to flush out that area with some type of solvent, kerosene, diesel, something that will wash out the gunk before you put something new into it.........Just old common sense.......God bless.......Dennis

  8. #8
    Benchwrenching PGlaves's Avatar
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    I need clearer terminology, so let's say transmission, driveshaft housing (swingarm), and final drive (rear end).

    If I understand correctly the transmission and driveshaft housing oil was fine - the final drive oil was cloudy like chocolate milk maybe.

    If so it is almost certainly water. Draining and refilling would still leave a coating of the gunk on the gears and walls of the housing, so a refill and re-drain would also look a bit cloudy but maybe not quite so bad.

    I do agree that a flush with a solvent like kerosene would be a good idea but with several caveats. Leave the key in the house. Do not turn the wheel with the engine. Leave the bike on the center stand.

    Drain the oil
    Fill with solvent to the normal level.
    Spin the wheel by hand as many times as you can stand
    Drain the solvent - leave the plug out till no drops are left to come out.
    Refill with 80w90 GL5 rated gear oil.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://www.bigbend.net/users/glaves

  9. #9
    #4869 DennisDarrow's Avatar
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    Quote Originally Posted by PGlaves View Post
    I need clearer terminology, so let's say transmission, driveshaft housing (swingarm), and final drive (rear end).

    If I understand correctly the transmission and driveshaft housing oil was fine - the final drive oil was cloudy like chocolate milk maybe.

    If so it is almost certainly water. Draining and refilling would still leave a coating of the gunk on the gears and walls of the housing, so a refill and re-drain would also look a bit cloudy but maybe not quite so bad.

    I do agree that a flush with a solvent like kerosene would be a good idea but with several caveats. Leave the key in the house. Do not turn the wheel with the engine. Leave the bike on the center stand.

    Drain the oil
    Fill with solvent to the normal level.
    Spin the wheel by hand as many times as you can stand
    Drain the solvent - leave the plug out till no drops are left to come out.
    Refill with 80w90 GL5 rated gear oil.
    One thing to add with Paul. That refill with GL5 gear oil, make it something cheap.....ride for a while, maybe 20 miles to get it hot, then let it drain and drain and drain..........THEN put in the good stuff.........God bless.......Dennis

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