QUESTION -parts interchangeability: 1100 GS final drive unit

Discussion in 'GS Boxers' started by Sjoerd Bakker, Feb 16, 2017.

  1. Sjoerd Bakker

    Sjoerd Bakker Long timer

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    My 1999 GS 1100, with ABS ,has the rear wheel Final Drive (FD) unit showing a marked amount of free play and there is a weeping of oil past the main seal (but no drips as yet) . It has been rebuilt once (in 2010 )after a big bearing failure . I have spent too much money on the bike already so I am considering the possibility of simply transplanting another COMPLETE used final drive (FD) unit onto it. If I could find one . These appear to cost much less than the shop time and parts I expect I would accrue in Canada.

    The problem is that on eBay I see a number of final drive units offered for R ,RS and RT models in the 1100 and 1150 series but NONE available for any model year of GS 1100 .Some of the FD units described for some earlier K-bikes appear to have the same basic casting shapes and ABS sensor port design. I tried all kinds of google search approaches but am not having any luck. I asked my BMW dealer where it was bought as new back when , but they are pleading ignorance.( should buy a new bike:rofl)There appear to be a number of variants of FD.
    My question is now for the knowledgeable GS initiates who may have DF parts cross reference charts, or personal experience with transplants.

    Is there such a thing as an FD unit with the ABS sensor port from ANY other model of BMW that would bolt straight in place , mate the splines , mount the brake caliper and require NO further accommodation ? I realize that the other 1100 models are more highway oriented and may have a slightly taller gear ratio of 33/12.
    That should not be a big problem as I never do any deep dirt riding with the bike , just gravel roads- at most ?

    What I have is a 1999 R1100GS ( model number ZC46827) with a final drive ratio stamp of 33/11 ,ABS and the brake rotor is fastened to the wheel (not on the FD !)
    On the inner face of the FD unit casting there is the number 2 320 121 BMW - see photo - which I imagine to be indicative of a production period or model run of that casting .
    Any help you may offer will be appreciated

    Attached Files:

    #1
  2. mouthfulloflake

    mouthfulloflake Not afraid

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    I think any 1100 FD from the same vintage would bolt on and fit, but only the GS has that 33/11 gear ratio ( the R, RS, RT bikes are not gear as low)
    #2
  3. rg sw wa.

    rg sw wa. Been here awhile

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  4. Drunk_Uncle

    Drunk_Uncle Long timer

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    The RT appears the same except for a different gear ratio and they are available new for both GS and RT. Pricey but piece of mind being brand new and believe some warranty especially if installed by BMW certified technician.
    #4
  5. slartidbartfast

    slartidbartfast Love those blue pipes

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    The FD's of that era swap like lego. Just be aware of the different gear ratios, as noted above.

    Changing the big bearing yourself is not a huge job. People have done it in a motel parking lot.
    #5
  6. Whale Rider

    Whale Rider Been here awhile

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    So what do you use the bike for if its just tar seal? then use a 1100 RT or 1150GS final drive good gearing for the black stuff 3750 rpm at about 60 mph. So in the early oilheads they changed the final drive ratios between the different models 99-2000 when the 1150 was introduced I believe they stuck with the 1 final drive 2.82 over the model range and changed the ratios in the gearbox. I have an 1100GS with a 2.82 on it for the road and first gear is the same as a standard 1150 6 speed 1st gear great all round bike.
    WR
    #6
  7. Sjoerd Bakker

    Sjoerd Bakker Long timer

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    Thank you all for the load of information you have supplied . The reference material provided by rg.sw.wa and the comments by Whale Rider go a long way to quieting my worries . Now I know that I can even consider an FD unit from an R1150 as substitute .
    The bike actually has been parked in the barn ( NO livestock !!:topes :D) under a cover the last six years after it dumped metal shim pieces in a gearbox oil change.
    That summer I did get a replacement tranny from the original selling dealer at a good price , but being a procrastinator I have not yet gotten around to doing that swap, went riding on another bike . Since the back end has to come off I figure it might as well get a less aged FD and make it a two -for -one project . I have been intimidated by the Haynes manual which does not delve into FD internals, saying that such is best left to expert technicians . I might even decide to take the FD apart first to see if the gears are worn( shouldn't be ,it ran fine ,no whining or bad noises like when the bearing failed ) I have been looking at the ADV tutorial about that rebuild and it suggests that fairly basic tools and techniques used with patience will suffice . If that job turns out badly :dunno I can still get a replacement FD .
    It being a closed gear unit I am still uninformed about how actually the bevel gears are kept in the exact required mesh engagement- shims ? or is it as a one-and-only-way decided by the case halves ? Back to the ADV tutorial videos .
    #7
  8. mouthfulloflake

    mouthfulloflake Not afraid

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    There are shims under the bearing, if it lead a long life, just re-use the shims as they are.

    If it failed early, you need to investigate further and possibly reshim at a different thickness to improve the gear mesh, and hopefully lengthen the bearings life.
    #8
  9. Sjoerd Bakker

    Sjoerd Bakker Long timer

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    Any opinions on this welcome; and a bit more background on the failures , possible cause
    The FD gave out in Guatemala ,about two days after I had an unintended very hard landing in a vado which suddenly appeared in an otherwise flat smooth paved sideroad in Nicaragua ( to VillaNueva) . I think the sudden square- on hard whack might have overdone it for the big FD bearing and considering the timing of the tranny spitting out thin flat sheet metal bits these might also derive from initiation in that same incident.
    The FD bearing and seal were replaced by Bavaria Motors in Guatemala City and total cost was (incredibly ) still under $200 US, so I have no complaints on that side ; it was an emergency repair and it got me mobile and home .
    But obviously when the FD began to show oil misting only 12000km after being repaired it was too early. Then again , the bike now has a total of 252800km on it , so maybe the tech in GT City could have reshimmed it but did not . Still, no complaint on them , they got me going quickly .
    My reason for considering buying a used FD are financial - around $200 and be done , with my labor.. Any time I take stuff in to the BMW shop here the bill comes to $1000 and up for the expensive new parts and the shop hourly rate .The FD will be no exception .
    #9
  10. rg sw wa.

    rg sw wa. Been here awhile

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    Suggest doing some searches on replacing the large seal on the left side / outside of the final drive and the large internal bearing. I didnt save the R & R procedures with pics that I used to do the job but am sure you can find it. I read the procedures a couple of times, looked at the pics and did the job. Now I bet you can even find the procedures on youtube. What usually fails internally is the large bearing and pieces of it can come out when you drain the oil.
    #10
  11. slartidbartfast

    slartidbartfast Love those blue pipes

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    Check in the Good Karma thread. Ricky is giving away boxes of early GS parts (probably the most reliable FD's) and there might be a FD amongst them.
    #11