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Thread: Final Drive Fluid, fill by measured volume or fill to level hole?

  1. #1
    Registered User Anyname's Avatar
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    Final Drive Fluid, fill by measured volume or fill to level hole?

    I've always filled the final drive on my 86 R80 monoshock until the level reached the overflow hole. This past weekend I tried using the 350cc volume the manual recommends. That turned out to be way more than needed to reach the overflow hole. So what do you all think? Is the measured volume correct or should I stick with the overflow hole?
    BMW R bike rider, horizontally opposed to everything...

  2. #2
    Registered User ebeeby's Avatar
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    Because the grease is quite viscous, you will find that running it a few miles will settle the grease and your fill will be low. You can warm the grease first to help it settle but you want to get that 350cc in there.
    1973 R75/5

  3. #3
    #4869 DennisDarrow's Avatar
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    For me, I fill to the bottom of the filler threaded hole threads. When I pop it open thousands of miles later it is sitting right there at the bottom of those threads. I do measure the amount of fluid in the engine; but the trans and rear end get the "thread" measurement technique. Now, the driveshaft, that's a different animal altogether........

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    Liaison 20774's Avatar
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    Quote Originally Posted by DennisDarrow View Post
    For me, I fill to the bottom of the filler threaded hole threads. When I pop it open thousands of miles later it is sitting right there at the bottom of those threads.
    I was going to say the same thing but our experience is with the pre monoshock rear drives. My Haynes suggests that fluid is poured in from the very top and you want the gear oil to be seeping out the inspection hole.
    Kurt -- Forum Liaison ---> 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!

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    #4869 DennisDarrow's Avatar
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    Quote Originally Posted by 20774 View Post
    I was going to say the same thing but our experience is with the pre monoshock rear drives. My Haynes suggests that fluid is poured in from the very top and you want the gear oil to be seeping out the inspection hole.

  6. #6
    Dances With Sheep GREGFEELER's Avatar
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    I attended the BMW Service School in 1974 and they said to the threads on the rear drive filler hole. This is not a critical measure. As long as there is at least 90% of the required volume of gear oil, and you don't over fill, you'll be fine.
    Greg Feeler
    Ambassador & amateur K-Bike collector, it seems
    1972 R75/5, 1990 K75, 1990 K1, 1992 K75S, 2003 K1200RS

  7. #7
    Registered User GTRider's Avatar
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    Over the years I’ve seen too many cases of stripped threads on the FD check plug on the bikes with the check plug screwed directly into the back side of the FD, and I continue to see them showing up at Tech Day. BMW used a small-diameter fine-threaded steel plug screwed directly into an aluminum housing with a crush washer for sealing, making it all too easy to strip those threads. And a proper repair in that area requires disassembly of the FD to assure no swarf is left behind. So for bikes equipped with that rear-mounted check plug, I drain the gear oil HOT, install the correct amount of gear oil through the filler hole, and button it up. Absent any visible leaks or excess gear lube showing up in the driveshaft tunnel, I don’t see a need to ever disturb that check plug.

    Best,
    DeVern
    Last edited by GTRider; 10-27-2020 at 02:04 PM.
    DGerber
    1983 R80ST 1984 R80 G/S-PD 2004 K1200GT w/Hannigan S/C 2010 K1300GT 2018 R1200GS
    BMWMOA#52184, AMA#271542, IBA#138

  8. #8
    Liaison 20774's Avatar
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    Greg -

    I think what you learned in service school was overtaken by events in later years. I agree that the filler plug at the 9:00 o'clock position when looking at the drive from the right side of the bike makes sense for refilling as you say. As DeVern says, that location had a change in later years to where it was a "check plug" not the filler plug. The filler location was located at the 12 o'clock position IIRC.
    Kurt -- Forum Liaison ---> 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!

  9. #9
    Quote Originally Posted by 20774 View Post
    Greg -

    I think what you learned in service school was overtaken by events in later years. I agree that the filler plug at the 9:00 o'clock position when looking at the drive from the right side of the bike makes sense for refilling as you say. As DeVern says, that location had a change in later years to where it was a "check plug" not the filler plug. The filler location was located at the 12 o'clock position IIRC.
    They took a perfectly good system in use for 50 years and "improved" it to a system that is flakey and fragile.
    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://web.bigbend.net/~glaves/

  10. #10
    Registered User 6322's Avatar
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    This thread reminded me of an old BMW rider I met in Detroit when I started riding BMWs in the early seventies. Fill to the bottom of the threads... The same was true of the /5, 6 and 7 transmissions. This guy would lay his bike over on it's side to get more oil into the trans. He figured if a little's good, a lot's better. Just glad I didn't take up his school of thought. I agree with using the prescribed, measured amounts. Never had a failure as a result.
    Gary Phillips - #6322
    Wildland Firefighter, Retired, Riggins, ID
    Heartland Moto Locos BMW Riders
    '77 R100/7 Dirt Hack, '83 R80ST, '85 K100RS w/EML, '93 K1100LT, '00 R1100RS

  11. #11
    Dances With Sheep GREGFEELER's Avatar
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    Quote Originally Posted by 20774 View Post
    Greg -

    I think what you learned in service school was overtaken by events in later years. I agree that the filler plug at the 9:00 o'clock position when looking at the drive from the right side of the bike makes sense for refilling as you say. As DeVern says, that location had a change in later years to where it was a "check plug" not the filler plug. The filler location was located at the 12 o'clock position IIRC.
    Yes, I was referring to the earlier rear drive design with the filler at the 9:00 o'clock position. Anything newer is a heresy and not a real BMW.
    Greg Feeler
    Ambassador & amateur K-Bike collector, it seems
    1972 R75/5, 1990 K75, 1990 K1, 1992 K75S, 2003 K1200RS

  12. #12
    Quote Originally Posted by GREGFEELER View Post
    Yes, I was referring to the earlier rear drive design with the filler at the 9:00 o'clock position. Anything newer is a heresy and not a real BMW.
    They had two young engineers and one old guy. The young fellows thought they needed something to do. The old guy suggested side stand design. They didn't like that. They wanted to do power train work. They decided to work on final drive design. The old guy said "No". The final drives were just fine.

    Then the old guy retired and the young fellows got promoted. Now they could redesign final drives. Their first act was the Airhead drives. After they "improved" the drain and fill for the Airheads they moved on to the Oilhead and later drives. They designed the drives for the K1200LT and the Oilheads. After those drives failed a lot they then designed the ventless, lifetime filled drives. Then they redesigned these to have a vent and a drain.

    Then they moved on to designing and specifying the camshaft and rocker arm designs for the R1200 series bikes.

    They are now senior engineers in charge of quality control and we are all in trouble. The end.
    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://web.bigbend.net/~glaves/

  13. #13
    Registered User ebeeby's Avatar
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    My point is that filling to the bottom of the threads is correct *IF* the grease has really settled in the drive unit which, if it is cool and the grease is thick, it often times will not do. Therefore, measuring out the correct amount and pouring it into the drive unit will indicate whether the grease has really settled and the unit really is filled to the bottom thread.
    1973 R75/5

  14. #14
    Liaison 20774's Avatar
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    ebeeby -

    I assume your "grease" equals "GL5 gear oil". Gear oil will flow slowly...grease not so much!

    What I do...and it probably doesn't make much difference...is after pour the gear oil into the fill hole on my /7, I spin the rear tire to see what happens to the level of oil. If needed, I can add a little bit. To be honest, as long as there's a reasonable amount of oil such that the crown gear is running through the oil, it's being slung all around for beneficial effect.
    Kurt -- Forum Liaison ---> 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!

  15. #15
    Registered User Anyname's Avatar
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    Quote Originally Posted by ebeeby View Post
    My point is that filling to the bottom of the threads is correct *IF* the grease has really settled in the drive unit which, if it is cool and the grease is thick, it often times will not do. Therefore, measuring out the correct amount and pouring it into the drive unit will indicate whether the grease has really settled and the unit really is filled to the bottom thread.
    My manual specifies 80-90 Gear oil. It's thick but by no means a grease.
    BMW R bike rider, horizontally opposed to everything...

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