Mysterious transmission creak - can't locate - need help!

horizon
horizon Posts: 91
edited August 2007 in Workshop
I've got a transmission problem on my Dawes Horizon which is driving me to distraction; basically I'm getting what's best described as a short sharp snap or creak sound intermittently, usually, but not always, after freewheeling and as I start to pedal again, sometimes, but not always, accompanied by what feels like the chain slipping and/or ghost shifting. I'm not pedalling hard when this happens, in fact I don't recall it happening when I am pedalling hard (not that I do often!). I have replaced the cassette, chain and chainwheels in an effort to eliminate it to no effect, in fact its made it slightly worse. The bottom bracket is an XT about 4000 miles old, the rear wheel a Shimano C201, 7000 miles old. Is the freewheel failing? I know my way around bikes reasonably wheel but this has me stumped. Any pearls of wisdom?

Comments

  • spasypaddy
    spasypaddy Posts: 5,180
    i am no expert in this stuff but if its starting again after freewheeling maybe its coming from your back wheel somewhere, as you've replaced the cassette maybe its the hub? i really really dont know though so dont go replacing something expensive on my say so!
    BMC TM01 - FCN 0
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  • Jonathan Mcp
    Jonathan Mcp Posts: 2,472
    Might be the freehub body, the splined part that the cassette fits onto. They can & do fail, I've hd one give way on a shimano LX hub but the good news is that they should be a replaceable item.

    The freehub is removed by stripping the axle & bearings out, then using a large allen key, can't remember size, but it is a big one, to basically unbolt it. I left it to my LBS to replace when mine failed, came in around £40 IIRC parts 7 labour.
  • horizon
    horizon Posts: 91
    Yes, its my suspicion that the freehub is failing and that was next on my list. However, just wanted to get some comments before I did in case its something simple (and cheap!)
  • passout
    passout Posts: 4,425
    That does sound like it to me.
    'Happiness serves hardly any other purpose than to make unhappiness possible' Marcel Proust.
  • horizon
    horizon Posts: 91
    Will be swapping out the freehub for a new one at the weekend; will report back.
  • horizon
    horizon Posts: 91
    Pleased to report that I've replaced the freehub with a new one and took the bike for a 25 mile shakedown yesterday and, praise be, no more noise! Not a job I've done before but it wasn't too bad. Spent a little time puzzling how to remove the hollow bolt from the freehub once it was away from the wheel; the dust cap was close to the ball bearings which in turn were holding the bolt in place. Looking at the replacement, the dust cap was nearer the face so I drifted the old cap away from the ball bearings and way to go. While I was at it I replaced the ball bearings both sides (and the front hub), no idea how long they last but while its all in pieces figured it was the right thing to do. Likewise, couldn't be doing with the faff of trying to resurrect the old one for the sake of £15. Always satisfying to be able to do these things oneself, thanks for the input.
  • Nigel Bennett
    Nigel Bennett Posts: 653
    Glad you've sorted it!

    I've just nailed an irritating creak - I'd changed the BB, pedals, and to ne effect. It turned out to be the pedal threads in the RH crank that had virtually stripped and the pedal was creaking about in what was left of the threads!

    Other sources of apparent transmission noise can be from the saddle - that caught me out similarly a while ago.

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