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Thread: Final drive and driveshaft service.

  1. #1

    Final drive and driveshaft service.

    1970 R75/5. Are the driveshaft and final drive both separate units? I see there are 2 fill bolts and 2 drain bolts. What would the capacity be on each? I've drained both, just don't want to fill incorrectly. Thanks

  2. #2
    The final drive fill just to the bottom of the threads where the fill plug screws in.

    There are lots of opinions about the driveshaft housing. The original BMW instructions called for adding oil and checking with a rod used as a dipstick with just a few millimeters of oil showing when the rod is inserted vertically. That is just a few millimeters above the splined coupling on the rear of the driveshaft.
    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/

  3. #3
    Liaison 20774's Avatar
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    Yes, separate reservoirs. For the driveshaft, specs call for 100cc...after the conversion to the long wheel base, it went up to 150cc, although even 100cc would work for the later driveshafts. As for the final drive, you remove the plug at the 9 o'clock position for filling...fill to the bottom of the threads.
    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!

  4. #4
    Day Dreaming ... happy wanderer's Avatar
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    Quote Originally Posted by clegg View Post
    1970 R75/5. Are the driveshaft and final drive both separate units? I see there are 2 fill bolts and 2 drain bolts. What would the capacity be on each? I've drained both, just don't want to fill incorrectly. Thanks
    Welcome to the MOA forum!

    According to the Clymer manual you should:
    - drain the warm oil and allow 15 mins to drain
    - screw in the drain plug (use only new crush washers and do NOT over tighten)
    - pour 100cc (0.21 US Pint)for /5 models of Hypoid gear oil 80/90. Make sure it is GL5 rated and NOT synthetic

    Same basic thing for the final drive:
    - drain the warm oil and allow 15 mins to drain
    - screw in the drain plug (use only new crush washers and do NOT over tighten)
    - pour 250cc (0.53 US Pint)for /5 models of Hypoid gear oil 80/90. Make sure it is GL5 rated and NOT synthetic

    If you don't have a manual consider getting one. These things are also in the owners manual but not procedures; only the data.
    Snowbum's tech pages have a plethora of information. Go here: http://bmwmotorcycletech.info/techni...icles-list.htm and scroll wayyyyyy down there for the list of articles.
    He makes ya work for it but the knowledge found there is exemplary and voluminous.
    MJM - BeeCeeBeemers Motorcycle Club Vancouver B.C.
    '81 R80G/S, '82 R100RS, '00 R1100RT

  5. #5
    Quote Originally Posted by 20774 View Post
    Yes, separate reservoirs. For the driveshaft, specs call for 100cc...after the conversion to the long wheel base, it went up to 150cc, although even 100cc would work for the later driveshafts. As for the final drive, you remove the plug at the 9 o'clock position for filling...fill to the bottom of the threads.
    Great info, thank you!

    I removed the hex head bolt at the final drive and the fluid was way overfilled, it was overflowing. Hence thinking that the driveshaft was with the final.

  6. #6
    Liaison 20774's Avatar
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    Quote Originally Posted by clegg View Post
    I removed the hex head bolt at the final drive and the fluid was way overfilled, it was overflowing. Hence thinking that the driveshaft was with the final.
    You might want to keep an eye on that. Once you fill with the proper amounts and the next time you decide to change fluids, the final drive overflows again, then you have a problem. There is a seal between the driveshaft and final drive. If it overflows, then fluid is getting past the seal.
    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!

  7. #7
    I just bought this non running. I got the engine running but have not ridden it. I will check the seal for sure. Thanks.

  8. #8
    Day Dreaming ... happy wanderer's Avatar
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    Quote Originally Posted by clegg View Post
    I just bought this non running. I got the engine running but have not ridden it. I will check the seal for sure. Thanks.
    Meh.. Checking the seal will involve removing the final drive. New gasket, new stretch bolts and really, when you remove it there is so much oil there already there is no easy way to know if the seal is leaking.

    Easiest thing to do and one should do this anyway is refill with known quantites of gear oil in the gearbox, drive shaft housing and final drive. When you next drain them ( I do them all at once since they all take the exact same stinky fluid) just look at the levels before you remove the drain plugs. If they are at the right approximate levels which is gearbox up to or very close to the lower threads of the fill hole, final drive about 1 to 3 mm above the level of the center of the shaft in the fill plug hole and final drive up to or near the bottom of the threads of the fill hole plug then you know the levels are OK.

    If you see a LOT more oil in the shaft than you put in or the final drive you know that it is migrating and you have a seal problem. And yes, gear box oil can migrate into the drive shaft housing if the rear seal of the gearbox is leaking.
    MJM - BeeCeeBeemers Motorcycle Club Vancouver B.C.
    '81 R80G/S, '82 R100RS, '00 R1100RT

  9. #9
    Liaison 20774's Avatar
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    Quote Originally Posted by happy wanderer View Post
    And yes, gear box oil can migrate into the drive shaft housing if the rear seal of the gearbox is leaking.
    Be sure the bolt that holds the speedometer cable to the right rear of the transmission has the hole down the center unplugged. This allows the transmission to breathe as fluids heat up and cool down. If plugged, the transmission can become pressurized and the fluid may migrate.
    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!

  10. #10
    Registered User ebeeby's Avatar
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    One other tip, when you fill the final drive to the bottom thread, give the wheel a bit of a turn. That grease is pretty thick cold, and sometimes willnot gravitate down all the way and oush out an air bubble leaving the final drive low on grease. Just turn the wheel a bit to get the gears to move and make sure the grease has settled and you are full to the low thread.

    And to emphasize, DO NOT OVERTIGHTEN any of the plugs. Use fresh crush washers and apply the right torque with a torque wrench (unless you have done it every week for 20 years and know what "a half-a-grunt" is)
    1973 R75/5

  11. #11
    Quote Originally Posted by 20774 View Post
    Be sure the bolt that holds the speedometer cable to the right rear of the transmission has the hole down the center unplugged. This allows the transmission to breathe as fluids heat up and cool down. If plugged, the transmission can become pressurized and the fluid may migrate.


    I just checked the speedo cable bolt. It is plugged. I have it in the ultrasonic now.

  12. #12
    Quote Originally Posted by clegg View Post
    I just checked the speedo cable bolt. It is plugged. I have it in the ultrasonic now.
    If you found excess gear oil in the swingarm and found the transmission vent (bolt) clogged it is highly likely that pressure in the transmission pushed gear oil past the seal into the swingarm. It is probable that clearing the clogged vent will cure the problem.
    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
    John D'oh
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    One of the problems threading a steel fastener into an aluminum fixture is the pressure on the aluminum threads fractures the fragile structure of the alloy if one applies too much torque or, in many cases, through just simply years of use. Your BMW motorcycle has several places you should be careful when tightening bolts and screws. In addition to the fill and drain plugs on the final drive there are threads in the vented speedometer clamp bolt boss on the back of the transmission (you just removed the bolt to open the vent)- those threads need to be in good shape to hold the battery ground tight and the speedo drive cable in place. Unfortunately that is the easiest to strip. Next in order is the oil pan drain plug followed by the oil pan mounting bolts themselves when replacing a pan with a stripped drain plug. There are three long cap screws that hold the stator housing to the front of the engine often semi-permanently -getting those loose, any one of them can ruin your day - completely. Oh yes - exhaust nuts. Use NEW crush washers/anti seize where appropriate and have at it. I don't know about others here but I've used 1/4" drive sockets and short handle wrenches for years to avoid over tightening and ease of working in tight confines. Oil migration has been covered previously.
    John D'oh

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