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  1. #1
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    Sport Shudders on Turns

    Does this happen to everyone with a Sport: flip it upside down, turn the steering, and then apply various amounts of throttle. Almost right away, mine begins to shake and shudder. There's a video of it on YouTube and a commenter says its normal for fixed diffs. Is that true? This is my first crawler.

    My car is new, only an hour of drive time on it. It's troubling and doesn't seem right to me. Is there anything that can be done about it? I can't see it while it's driving, but it is surely happening and seems destructive to the drivetrain.

  2. #2
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    Could you link the video you referenced so we can better understand what you are describing.


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  3. #3
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    At the maximum steering it is normal, for all trx-4's. It's due to the steering knuckle's angle, not to the locked axle.
    It's not noticeable when driving, only with it upside down :-)

  4. #4
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    Quote Originally Posted by BadBeard258 View Post
    Could you link the video you referenced so we can better understand what you are describing.
    Sure
    https://youtu.be/b8ry3CdoRK4

    The behavior starts at 14 second mark. Mine does this too, except I'm able to reproduce it much faster than the video, and it doesn't need to be full throttle. Unfortunately, they pan the camera to the shafts once it begins, but you'll get the idea briefly. With mine, it sounds like it's coming from the front axel.
    Last edited by JohnnyCarlos; 09-28-2018 at 06:59 AM.

  5. #5
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    Quote Originally Posted by Bert 1100 View Post
    At the maximum steering it is normal, for all trx-4's. It's due to the steering knuckle's angle, not to the locked axle.
    It's not noticeable when driving, only with it upside down :-)
    So it sounds like nothing can be done about it. My concern is that it's doing some damage. Do you all avoid maximum steering angle? How long is it before those parts need replacement?

  6. #6
    RC Turnbuckle Jr. Greatscott's Avatar
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    All normal.

    The U-Joints at the steering knuckles can only operate to a certain angle, then they start skipping, the TRX4's steering takes them just beyond that angle. Someone will have to come out with a CVD kit to correct this issue. Given that there have been few reported failures of the front drive shafts, I would say that it really is not an issue. Plus, you just don't have the steering at full throw very often for trail running. I crawl with mine, and have the steering at full throw quite a bit, and I have not seen any abnormal wear and have not had any breakage in the front axles, and this is running with a Mamba X and 1900kv motor on 3S.
    Submarine Qualified, Chief Inducted, Navy Retired

  7. #7
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    Quote Originally Posted by Greatscott View Post
    All normal.

    The U-Joints at the steering knuckles can only operate to a certain angle, then they start skipping, the TRX4's steering takes them just beyond that angle. Someone will have to come out with a CVD kit to correct this issue. Given that there have been few reported failures of the front drive shafts, I would say that it really is not an issue....
    Ah, ok. I see now and feel better about this. I took some keywords out of your reply, did some searches, and came up with this explanatory demo:
    https://www.youtube.com/watch?v=Idk3BVDVHq4

    I had noticed that the wheels were not rotating at a constant rate while it was shuddering and was bothered that gears or something might be slipping.

    Learned something new today. Thanks!

    I will surely be on the lookout for a CVD kit. That is a must upgrade. Any disadvantages to them?

  8. #8
    RC Turnbuckle Jr. Greatscott's Avatar
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    They are used on other crawlers, they allow for shaft rotation at a tighter angle. Sadly, I have not seen a kit out yet for the TRX4. Hopefully MIP or Vanquish will produce one.
    Submarine Qualified, Chief Inducted, Navy Retired

  9. #9
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    Oddly, my Defender does not have this problem. I can turn lock to lock, at full throttle, while upside down, and still no shaking. I have put quite a bit of wear on my TRX-4 though. That might be it. The only shaking I have is when the tire flexes and rubs on the springs or the body..
    Guess who's back.
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  10. #10
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    Quote Originally Posted by Sprinkletron View Post
    Oddly, my Defender does not have this problem. I can turn lock to lock, at full throttle, while upside down, and still no shaking. I have put quite a bit of wear on my TRX-4 though. That might be it. The only shaking I have is when the tire flexes and rubs on the springs or the body..
    Were your front diffs locked when you tested it?

  11. #11
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    Quote Originally Posted by JohnnyCarlos View Post
    Were your front diffs locked when you tested it?
    They were but my diffs have been acting a little funky lately and the servos aren't fully locking the diffs. That's probably it. I'll probably switch to spools here soon.
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  12. #12
    RC Turnbuckle Jr. Greatscott's Avatar
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    Just saw this...

    https://www.youtube.com/watch?v=umePyJznyPs&t=411s

    (it should start around 6:45)

    Found them on Traxxas' site:

    https://traxxas.com/products/parts/8062
    Last edited by Greatscott; 10-03-2018 at 07:12 PM.
    Submarine Qualified, Chief Inducted, Navy Retired

  13. #13
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    Great Scott!

    Very nice find, thank you. Now that I know what it is, I'll leave them be for the time being, especially for $60. I'm an upgrade as it breaks type of person. I think.

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