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  1. #1
    RC Competitor
    Join Date
    Mar 2012
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    56

    Is there a part upgrade for the spur gear shaft "roll pin"?

    A friend has a 2wd slash with velineon motor.
    He has broken a few of the "roll pins" that hold the spur gear to the shaft. They "shear" off.
    Is there a recommended upgrade for this? or should it just be allowed to be the best weak point?
    4x4 Ultimate (Slayden Suspension<Big Improvement!)

  2. #2
    RC Turnbuckle Jr. Greatscott's Avatar
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    Mar 2004
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    N. Idaho... Da Sticks!
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    3,065
    This is not a common problem...

    The weak point in your drive train, by design, is your slipper clutch. If you are shearing any pins in your drive train you likely have two problems:

    1- Your slipper clutch is set too tight and is not being allowed to do its job of protecting the drive train.
    ---- As a starting point, tighted the clutch down all of the way, then back off 1/4 turn.

    2- It sounds like your spur and pinion are set too far part giving a lot of backlash, which shocks the drive train when you are hard on the throttle, or go to full breaks/reverse.
    ---- The old school of thought for gear mesh was to have just enough room for a piece of paper to slide between the gears, this is no longer the case, the experts say it puts in too much backlash. You want your gears as close as you can get them, without binding your drive train.
    Last edited by Greatscott; 03-11-2012 at 12:38 PM.
    Submarine Qualified, Chief Inducted, Navy Retired

  3. #3
    RC Champion
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    Feb 2009
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    Quote Originally Posted by Greatscott View Post
    ---- As a starting point, tighted the clutch down all of the way, then back off 1/4 turn.
    just because everyones cars are set up differently, we already know its too tight so I would just back it off from where its at

  4. #4
    RC Champion
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    Nov 2011
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    North Central OH
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    Has he modified the stock differential at all, is it still an open diff?

    I have read several threads where the the pin has sheared and it may be due to it drifting out of the hole more so than being sheared from too much backlash as you would be more likely to shear pinion and spur teeth before the steel gear on the top shaft.

    I would put a new shaft/pin and gear in it and see if that doesn't fix it. That top gear is a press fit that indexes onto that pin, it is very tight but I suspect the pin is slipping out then getting mulched. If the slipper was ever overheated it may have damaged the integrity of fit for the entire shaft.

    Full brakes/reverse on a high traction surface is definitely gonna cause breakage, the weakest link will show up first

  5. #5
    RC Competitor
    Join Date
    Mar 2012
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    56
    OK, Thanks guys,

    I've sent this info to him about this, and hopefully he will remedy the issues.

    Thanks for the help!
    4x4 Ultimate (Slayden Suspension<Big Improvement!)

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