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Diff output shafts

Discussion in 'Gearboxes and drivetrain' started by cobraboy, Nov 11, 2017.

  1. cobraboy

    cobraboy Active Member

    Any one know why there is a step in the splines on the diff output shafts ?
    Does this serve any purpose, I cannot see that it has any implications for the lateral location of the shaft and if it is a fatigue point why cant the step be smoothed over a longer area ?

  2. Vern Klukas

    Vern Klukas Member

    I don't know why the relief is there, but it's not the fatigue point. The shafts fail where the spline exits the side gear.

  3. cobraboy

    cobraboy Active Member

    Thanks Vern
    I was told that the shafts break at the step, is this not where they exit the planet gears ? having not been into a diff yet I am trying to get a head start on any problems.

  4. harveyp6

    harveyp6 Well-Known Member

    They will snap anywhere....

  5. Vern Klukas

    Vern Klukas Member

    The step is a bit further on from where the shaft exits the gear. To be honest, I think the reduced diameter from the step is actually reducing the stress, as the failures alway occurred with the very top of each spline starting to crack, and the crack then progresses down the spline flanks until it get to the solid body of the shaft and tears through. To my mind the solution would of been to reduce the spline length so that the entire spline is within the side gear.

  6. cobraboy

    cobraboy Active Member

    OK kind of makes sense, a shorter spline that has a slope up to the larger plain diameter.

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