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Thread: Final Drive Failure

  1. #21
    Join Date
    Apr 2007
    Location
    Birmingham
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    716

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    Quote Originally Posted by FLATRABBIT View Post
    Jamie,
    How many miles were on your final drive when it failed? I change the oil in the final drive when I change engine oil on my LT. (Knock on wood), I am hoping this will add some life to my final drive.
    My first one failed at 30k, the second one failed at 77k. I change the gear oil every other time I change engine oil. I don't believe the frequency of oil change will have any effect on the life of the crown wheel bearing. After all, most people never change the gear oil in the differential of their rear wheel drive auto, and go for several hundred thousand miles without failure of any kind.

    I think the problem is a combination of design flaw, poor quality of bearings that are outsourced from who knows where, and poor assembly of the final drives. But what do I know...
    Jamie
    02 K1200lt
    82 R100RT

  2. #22
    Join Date
    Mar 2009
    Location
    Jasper, Alabama
    Posts
    90

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    Jamie,
    Thanks for the informative thread from all of us who live in fear of the dreaded final drive failure. Did you consider the Rubber Chicken Racing bronze bushing bearing replacement? http://rubberchickenracinggarage.com/bushing.html It seems to address the side loading issues that you mentioned. Some on the national BMW forum say that this is a bogus replacement, but it seems to make sense to me. The only thing that seems negative about it is that he recommends a 10 to 15 k inspection and re-grease. Though compaired to an unexpected catastrophic failure on the road the extra maintenance may not be so bad after all.

    Jeff Sparks
    R1150R

  3. #23
    Join Date
    Apr 2007
    Location
    Birmingham
    Posts
    716

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    Jeff, I think we are talking about two different issues. The bronze bushing that is referenced on that web site replaces the two small bearings that provide the up and down travel of the final drive in reference to the drive shaft housing (paralever).

    The final drive failures that I, and hundreds of others, have experienced is due to complete failure of the very large crown wheel bearing located inside the final drive housing, and functions as one of the "axle" bearings. The other "axle" bearing is located on a shaft on the other side of the crown wheel, and is a tapered bearing much like the front wheel bearings in a Chevy, or Ford, pickup truck. The tapered bearing is the one that must be preloaded from pressure exerted by the case pushing against the crown wheel bearing. This preloading method is what causes the very high side loading of the crown wheel bearing.

    I certainly am not an engineer, but it seems to me that if the crown wheel bearing was a tapered roller bearing then preloading would have no adverse effect on either bearing.
    Jamie
    02 K1200lt
    82 R100RT

  4. #24
    Join Date
    Apr 2007
    Location
    Birmingham, Alabama
    Posts
    1,837

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    Quote Originally Posted by Bikebum View Post
    I certainly am not an engineer, but it seems to me that if the crown wheel bearing was a tapered roller bearing then preloading would have no adverse effect on either bearing.

    Baloney Jamie.

    BMW should hire you to head up their engineering department
    Bob Steber
    1995 R100GSPDC Long Tall Sallie
    1976 R90s Odalisque

  5. #25
    Join Date
    Oct 2008
    Location
    JASPER, ALABAMA
    Posts
    73

    Default Final drive solution

    Jamie,
    You are more experienced and knowledgeable about BMW Motorcycles than I am. You have probably forgotten more than I know about them. I value your comments and opinions highly.

    I have never been inside the final drive of my bike (or any other K1200LT); however, I was wondering is there a threaded collar for the crown bearing that can be tightened in order to take any "slack" out of it. (Just wondering). Sorta like the nut that tightens the wheel bearing on a car.

    Regardfs,

  6. #26
    Join Date
    Apr 2007
    Location
    Birmingham
    Posts
    716

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    The "nut that tightens the bearing" is the cover on the rear drive housing. The amount of "tightening" (preload) is determined by the shim(2) thickness between the bearing(3) and housing cover(5 in second illustration). The preload is to assure that the tapered roller bearing(5 in first ill.) is snug in its race.

    Crown Gear and Shims.jpg

    Housing.jpg
    Jamie
    02 K1200lt
    82 R100RT

  7. #27
    Join Date
    Mar 2009
    Location
    Jasper, Alabama
    Posts
    90

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    Jamie,
    Thanks again for the informative thread. I hope to avoid first hand experience with the final drive but now I have more understanding about the issue. It kind of makes a swing arm with two sides and nasty old chains and sprockets not seem so bad. I hope the engineers updated and beefed up the final drive on the 160 HP K1600GT and GTL.
    Jeff Sparks
    R1150R

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