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Thread: Final drive vent

  1. #1
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    Final drive vent

    Just went on a spirited three day ride on my 1982 R100 RT, running around 4000 rpm most of the time and a lot of 70 mph stints. The final drive vent throws so much oil it is ridiculous. Every time we stopped i had to wipe things down. I had oil all over the rear tire. The fluid levels were correct to start the ride. There just is no splash guard for the vent. When i look into the boss for the vent, i see the gears. This is a horrible design. Has anyone else had this issue? How did you resolve the issue? I just tried a fix. I'll let you know if mine worked when i take it out next time.

    Thanks,
    Jim O'Coin
    1982 R100RT
    1971 R75/5

  2. #2
    Registered User wvpc's Avatar
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    As the owner of an 83 RT for 3 decades I have never had a catastrophic FD leak. Has the FD been serviced lately? You don't say how many miles are on the bike. Maybe the inexpensive vent plug is faulty? Get a new vent plug and re-service the FD with fresh lube and crush washers.

    Good Luck.
    Last edited by wvpc; 08-21-2013 at 03:33 PM.
    12 R1200 RT
    83 R100 RT

  3. #3
    Registered User toooldtocare's Avatar
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    You said the fluids were the correct level, so this may not be the problem, but on my R90S the same thing happened. Turned out to be the seal on the input shaft to the rear end. Mine went bad and allowed the oil from the drive shaft flow into the rear end, over filling it. A very simple repair.

    Wayne

  4. #4
    Administrator 20774's Avatar
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    What gear oil are you running?
    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!

  5. #5
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    Just hit 56k miles. I serviced the final drive for driveshaft oil migration two years ago and i know this is not an issue. Should there be a splash plate inside the final drive? That would be the only way to prevent me from seeing the gears. There is no splash plate inside the vent plug. I have been using 80w90 gear oil.

    Thanks
    Jim

  6. #6
    Registered User lmo1131's Avatar
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    You serviced the final drive for driveshaft oil migration two years ago ... conditions do change. Obviously this isn't a "normal" condition; something has failed and is allowing oil to migrate into the FD. There is no splash plate. As mentioned, the shaft seal (#5) has more than likely given up the ghost.



    There are two "weep" holes that may be obstructed. They aren't intended to drain excessive amounts of oil, so you will still need to investigate the cause.

    One below the axle nut,



    the other is adjacent to the drain plug (leading to the spline area).



    Source: http://w6rec.com/duane/bmw/finaldrive/

    Alternatively; you may want to consider rigging a puke line.



    Source: http://www.advrider.com/forums/showthread.php?t=237546
    "It is what you discover, after you know it all, that counts." _ John Wooden

    Lew Morris
    1973 R75/5 - original owner

  7. #7
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    I dont think oil is migrating from the driveshaft. I did a fluid check upon comming home. Still near the correct amount of oil in the driveshaft. Fluid in the final drive was probably a half inch below the drain bolt at 9:00. Where does the "puke" line run to? I like that idea. I could run it such that any oil that made to the puke line could drain back to the final drive.

    Thanks
    Jim

  8. #8
    Administrator 20774's Avatar
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    I would think the right thing to do is find out why it is puking...it's not one of those "they all do that" kind of things. Something is wrong if it's blowing oil. How's the oil level in the tranny? How does one check the oil level in the driveshaft? I remember seeing some approach in my old Clymers about sticking something around the driveshaft but I thought that was all bogus. I just drain and refill with the right amount...I never check it.
    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!

  9. #9
    24991 Pauls1150's Avatar
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    Clymer's had this one right; it was also in the owner's manual. There was a thin metal rod included in the toolkit for this. One stuck it down the filler hole, found the little "dip" that it dropped in to, and the oil was supposed to be 1/8" up the stick.

  10. #10
    Registered User PAS's Avatar
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    Is it safe to assume your RT has a rear disc brake, if so the vent holes are not as shown. My 81 has never puked oil and it has 165K on it. I use an 80-90 gear oil.

  11. #11
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    NOT a design malfunction to not have a splash guard, as oil will not try to migrate out if filled to the correct level. You are not puking oil due to a "splash" condition, you are losing oil due to excessive oil finding its way into the FD. Either due to initial overfill, migration from the shaft past the seal, or from the trans and then past the seal.
    Find and fix the cause, rather than treating the symptom.
    A small amount of oil can make a big mess. I'm voting for the shaft seal, with migration direct from the shaft itself.
    Ride Safe, Ride Lots

  12. #12
    #4869 DennisDarrow's Avatar
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    Quote Originally Posted by Pauls1150 View Post
    Clymer's had this one right; it was also in the owner's manual. There was a thin metal rod included in the toolkit for this. One stuck it down the filler hole, found the little "dip" that it dropped in to, and the oil was supposed to be 1/8" up the stick.
    +1 on this! From the owner's manual, page 59, the directions clearly state to check the driveshaft oil by inserting a metal rod, such as a screwdriver, into the oil filler hole and allow the rod to come to rest on the shaft. The correct level is 2 mm. For me, I have used this method for many checks by using a broom straw. Anyway, I really agree that one needs to find the cause of the problem and not just treat the symptom.........God bless......Dennis

  13. #13
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    All good theorys but i said the driveshaft is not loosing oil. The tranny is fine too. The damn vent plug has three holes at the very top covered by an exterior cap. Oil splshes up there, makes it way through the three holes and blows out everywhere. Like i said the final drive was 1/2" below the 9:00 drain hole. And the drive shaft still had close to the right amount of oil. I guarentee the final drive lost more oil than i put in the driveshaft to begin with. That is not the problem. What is the inside of the vent cap suppose to look like? I can't believe nobody has had this problem before. Oh, yes, rear disk brake.

  14. #14
    Administrator 20774's Avatar
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    A picture of your setup, like an overall exterior shot and maybe something closer up showing more detail might help us get a better idea. As has been said, this is not a typical problem, so there's something unusual about your configuration.
    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!

  15. #15
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    I can't figure how to upload photos of mine, it keeps failing. I think they are too large in size. I found this picture which is just like mine.
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