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Thread: Drive shaft noise ??

  1. #1
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    Drive shaft noise ??

    1985 R80,

    Just before going to Daytona last week i noticed a slight clunk coming from the drive shaft area of the bike while pushing it in the garage. No other oddities , vibrations or noise, just a clunk sound moving forward or backward.

    By the time I got to Daytona the sound was a bit louder and there may have been some additional vibration, but that's hard to tell.
    Rode it all week , had a couple guru's listen to it , and they are pretty sure it sounds like a bad U joint ??

    I had no alternative but to ride it home, kept checking it at every stop. The final drive housing, shaft and boot did not feel hot to the touch. No fluid leaks, and i had recently changed all the fluids . They are all up to spec level still and do not smell funny or appear to be burnt.

    I have never torn in to the rear drive assembly on the bike so please bear with me as i will have lots of questions as i go. The parts fische does not show the U joint as being a service part and the drive shaft assembly is predictably BMW. "expensive".

    Who has a source for rebuilt units ???

    Any suggestions on what to look for or check as i take it apart ??
    Thanks, Doug

  2. #2
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    Look first at the bolts holding the U-Joint to the back of the transmission.
    These can come loose and make a clunk noise for some time before one drops out and causes damage.

    One who has had one of these apart and knows what to feel for can feel of the joint and bolt heads through the rubber boot as the wheel is slowly rotated and detect loose bolts or sloppy U-Joint.

    With no experience you will probably have to drain the driveshaft and pull the boot back from the transmission to inspect the U-Joint and its bolts.

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    A friend had the same noise in his 85 R80(build date Jan 85). He pulled the boot back and found the UJoint worn. The driveshaft is in CA being rebuilt.
    Ron

    91 K75RT ABS

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    roncooper,
    Do you have the name and e mail address of the shop rebuilding your friends drive shaft ??

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    Ron

    91 K75RT ABS

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    Danke !

    I bookmarked the page , later in the week when i am over this head cold i will start tearing the Bavarian bastich apart and see what evil lurks within.

    Doug

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    later in the week when i am over this head cold i will start tearing the Bavarian bastich apart and see what evil lurks within.
    Whoa, whoa, whoa... talk nice. What did the old comrade do to you, besides haul you over a thousand miles, and get you back home without locking up and spitting you off onto the side of the road?

    BTW, +2 on Henderson, they rebuilt the u-joint on my '73 /5. Excellent work, high quality materials and excellent communication. $160 + shipping.

    Remember to replace the four 12pt. u-joint bolts. Might as well replace the boot too while you're down that far (you're not really going down that far on this job).

    Here's the rebuild
    "It is what you discover, after you know it all, that counts." _ John Wooden

    Lew Morris
    1973 R75/5 - original owner

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    Quote Originally Posted by 40427 View Post
    Danke !

    I bookmarked the page , later in the week when i am over this head cold i will start tearing the Bavarian bastich apart and see what evil lurks within.

    Doug
    You will need to modify a 27mm socket or buy one already modified. This is for the swingarm pivot locknuts. You will also need a 12 point 12mm socket for the nuts that hold the final drive to the swingarm.
    Ron

    91 K75RT ABS

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    Quote Originally Posted by roncooper View Post
    You will need to modify a 27mm socket or buy one already modified. This is for the swingarm pivot locknuts. You will also need a 12 point 12mm socket for the nuts that hold the final drive to the swingarm.
    The driveshaft assembly is one of those areas where you should use NEW screws (special 12pt. M8) on reassembly every time, along with Loctite ÔÇ£BlueÔÇØ. You might also look at purchasing a torque wrench adapter/extension that will give easy access and allow you to torque the screws correctly (the extension means that there is some math to do to equate the torque indicated on the wrench to the torque applied to the screw). A simple tool that makes for a very easyjob. I got mine from Northwoods (see: http://www.northwoodsairheads.com/Tools.html), but there are other sources.

  10. #10
    Monza Blue 1974 R90/6
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    I don't know exact difference between my R90 and your R80, but if they are close, then the modified 27mm socket is the only special tool you really need. If you have the 10mm box combo wrench from your tool kit, it works really well with the driveshaft bolts.

    Remove the clamp holding the boot to the transmission and pull it back so you can get your fingers in and push/pull sideways on the driveshaft to see if the u-joint is failing. You can also examine to bolts holding the shaft to the transmission flange (transmission in neutral, bike on center stand and rotate rear wheel to bring each bolt around where you can see it).

    There was a thread here not long ago about a clunk-clunk that was the result of the swing arm being off center and the u-joint hitting the swing arm. You'll be able to rule that out at this point as well.

    If you decide to take things apart, use the rear brake to hold everything in place while you loosen the bolts holding the drive shaft to the transmission flange. Once you get them loose it is tricky to get them out with your fingers without dropping them down inside the driveshaft housing.

    With all four bolts off (on my model bike) you have to remove the rear brake pedal and rod assembly, then you need the modified 27mm socket to remove the swing arm lock nuts, and a large Allen wrench to remove the pins.

    Next steps really depend on what you want to do next.

    On reassembly, I agree with the advice to use new bolts and blue loctite. But, I don't know if you need the special torque adapter. The box wrench you used to disassemble seems to work fine with just a good grunt for tightness.

    Barron

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    Thanks for the clear explanation Barron.

    Why is it necessary to replace the drive shaft bolts with new ones ??

    Seems logical that if they come out easily and you add some fresh blue locktite they should be re-usable.

    Unless they are some kind of a special application bolt that is only good for one time use ?

  12. #12
    Monza Blue 1974 R90/6
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    My understanding is that they stretch when tightened.

    Barron

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    Quote Originally Posted by 40427 View Post
    Thanks for the clear explanation Barron. Why is it necessary to replace the drive shaft bolts with new ones ?? Seems logical that if they come out easily and you add some fresh blue locktite they should be re-usable. Unless they are some kind of a special application bolt that is only good for one time use ?
    Quote Originally Posted by Barron_Williams View Post
    My understanding is that they stretch when tightened.
    Seemingly, the screws (no nuts, therefore screws not bolts in my book) are a hardened grade. Also, BMW, apparently say not to reuse old driveshaft screws. Gurus seem to be divided on the matter. I follow BMWÔÇÖs advice. Worst case scenario is that I ÔÇ£wasteÔÇØ $6 for four new screws from BMW.

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    Got it, thanks !

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    Quote Originally Posted by 40427 View Post
    Thanks for the clear explanation Barron.

    Why is it necessary to replace the drive shaft bolts with new ones ??

    Seems logical that if they come out easily and you add some fresh blue locktite they should be re-usable.

    Unless they are some kind of a special application bolt that is only good for one time use ?
    don't worry as much about bolts coming out easy, but do they go back in easy? if so, yeah, nothing wrong with reusing with blue loctite.
    "best practice" is to replace, but no need to go frantic if all you can do is blue loctite.

    if you fumble the bolts trying to get them in or out of the setting, and you drop one, they are nearly impossible to drop down the driveshaft housing. much more likely is that they go into some annoyingly bothersome recess of the d/s boot. magnet works well for extracting.
    given that the noise started up out of nowhere, i'm thinking either 1 or 2 of those bolts have worked loose are are clanking about, or you have a wornout u-joint.
    Ride Safe, Ride Lots

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