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Thread: Crunch-shifting

  1. #1
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    Crunch-shifting

    I noticed that if I shift from low to high gear while stopped, the Summit puts out this nasty crunch/grind sound even using extremely slow accelleration afterwords. It happens about 50% of the time, and about 25% of the time it won't actually change from low to high. High to low works awesome. The manual says that you can shift while moving, should you only shift while moving? Anyone else have this issue?
    Monstered Slash/Mamba Max - Stock Summit

  2. #2
    RC Turnbuckle Jr. danielhr77's Avatar
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    You can shift while moving, but release the throttle for a moment while doing it... About the sound, I don't remember that sound on my E-Maxx, for example...
    He Who Dies With the Most Toys Wins.

  3. #3
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    I don't hear a crunch in mine when I shift?
    Traxxas Rally, Grave Digger, and LaTrax Alias

  4. #4
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    I would think you would want to shift while moving.
    I recall the manual suggesting down shifting when going around 5mph. I don't remember seeing a suggestion for up shifting.
    During the half hour of running my Summit I always had it running slowly when shifting and never heard any extra sounds.

  5. #5
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    On mine it is LOUD, like bones grinding. I replaced 5678 in my rear diff, but other than that it is stock. I guess I'll drive it until it breaks and then call traxxas support....
    Monstered Slash/Mamba Max - Stock Summit

  6. #6
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    Quote Originally Posted by Koko
    I don't hear a crunch in mine when I shift?
    Your asking us?

  7. #7
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    Quote Originally Posted by Mad_Dawg
    On mine it is LOUD, like bones grinding. I replaced 5678 in my rear diff, but other than that it is stock. I guess I'll drive it until it breaks and then call traxxas support....
    Did it happen before and/or after the 5678 replacement?

    Maybe something is out of alignment or there's a chipped tooth?

  8. #8
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    It happenned after the 5678 replacement, but I didn't touch anything forward of the rear bulkhead. I think some water got in the tranny during the run that broke 5678. I took it for a spin at lunch and it looks like part 3989X which the servo uses to switch gears isn't getting pushed all the way in when switching to high gear (water damage?). I think that is causing both gears to be engaged for a moment while 3938X gets settled, causing the crunchiness. I'll manually help the servo this evening and see if that takes care of it.
    Monstered Slash/Mamba Max - Stock Summit

  9. #9
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    As an update, the grinding issue has been resolved. I neglected to put the drive shaft cover back on after testing the gear mesh after my 5678 replacement. It works like a champ now.
    Monstered Slash/Mamba Max - Stock Summit

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