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  1. #1
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    Pinion is still sliding around...

    I just got done putting two packs through my Slash 4x4 and the pinion is still moving down the motor shaft. I just can't figure it out. The thing starts out SUPER tight but loosens right up after a few minutes. Yes I've tried blue Loctite. Yes I've tried red Loctite. No... none of them have worked. I'm almost to the point of welding the darn thing in place.


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  2. #2
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    Haha I had the same problem. Blue loctite worked for me.

  3. #3
    RC Turnbuckle Jr. kdvanb's Avatar
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    Try a new pinion?
    Slash 2wd, Slash 4x4, 30th digger, Rustler VXL

  4. #4
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    Thats really strange. Has the motor shaft become tapered? Are you torquing it enough?
    The only time Ive had them come loose is not using blue loctite and the grub screw backing out. If it came loose with red loctite and you were still able to get the screw out then the red loctite is water colored with red food dye. I only use that stuff on something I never intend on taking off again as once its set its a real PITA to get out, usually requires heating it up.
    Didnt you post that it had red loctite when you got it and had a hard time getting the grub screw out? may have been a reason for that. Id bee looking really close at the motor shaft and the pinion.

  5. #5
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    Quote Originally Posted by JustinThyme View Post
    Thats really strange. Has the motor shaft become tapered? Are you torquing it enough?
    The only time Ive had them come loose is not using blue loctite and the grub screw backing out. If it came loose with red loctite and you were still able to get the screw out then the red loctite is water colored with red food dye. I only use that stuff on something I never intend on taking off again as once its set its a real PITA to get out, usually requires heating it up.
    Didnt you post that it had red loctite when you got it and had a hard time getting the grub screw out? may have been a reason for that. Id bee looking really close at the motor shaft and the pinion.
    I'll have to get the micrometer and measure the shaft I guess. I haven't tried to take the grub screw out since I put the red stuff on. It never had red Loctite on it before. I bought it new.


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  6. #6
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    OK must have been someone else posting about that. My bad, they got a truck with red locktite and had to cut the pinion off the shaft. If the grub isnt moving at all then it has to be either the motor shaft or tin inner bore of the pinion.

  7. #7
    RC Turnbuckle Jr. El Sob's Avatar
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    If I were you, I'd super glue it on there. Let it dry for a full day and you should be fine. I mean glue it to the shaft!
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  8. #8
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    Quote Originally Posted by El Sob View Post
    If I were you, I'd super glue it on there. Let it dry for a full day and you should be fine. I mean glue it to the shaft!
    I think I might. I hate to weld it and ruin a motor shaft but I've never changed pinions on the thing because it runs so good out of the box so I doubt I'd ever want to take it off... it's just worth less if I were to sell it. Superglue would be able to be burnt off.


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  9. #9
    RC Turnbuckle Jr. El Sob's Avatar
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    If I were you, I'd super glue it on there. Let it dry for a full day and you should be fine. I mean glue it to the shaft!
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  10. #10
    RC Racer
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    Try a new pinion pal... what pinion brand are you running? I had the same problem with a Traxxas pinion...It didnt worked because of a ruined inner thread of the pinion. The grub screw was ok and tight when I screwed it....

  11. #11
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    Take the pinion off the shaft and screw the grub screw all the way down. Make sure it goes down far enough. It might even fall through. I had one that did the same as yours, turns out it was just barely tight enough to hold. With the pinion on the shaft it felt like it was as tight as I could get it.

  12. #12
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    Quote Originally Posted by Beholder_74 View Post
    Try a new pinion pal... what pinion brand are you running? I had the same problem with a Traxxas pinion...It didnt worked because of a ruined inner thread of the pinion. The grub screw was ok and tight when I screwed it....
    You could be on to something. It's the stock Traxxas pinion. I've tried probably 8 different grub screws from 3 different brands but that wouldn't make a difference if the threads are bad right before the screw hits the shaft.


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  13. #13
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    Quote Originally Posted by briandee View Post
    Take the pinion off the shaft and screw the grub screw all the way down. Make sure it goes down far enough. It might even fall through. I had one that did the same as yours, turns out it was just barely tight enough to hold. With the pinion on the shaft it felt like it was as tight as I could get it.
    I second this idea. It's possible the threads on the pinion are not good all the way through. The set screw could be stopping short of the motor shaft giving you the illusion that it is tight when it really isn't.

  14. #14
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    Also a little blue loctite o the shaft and grub never hurts


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  15. #15
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    What I did is that I tried putting the screw in the pinion when it wasn't on the shaft and I realized that the grub screw area was stripped! Get a robinson racing pinion 13 tooth and buy a few extra grub screws, then (off the shaft) tighten it until you see it peek out through the small hole where the shaft goes in. Take the motor off the car, and install the pinion with the grub screw on the flat side of the shaft and try it without connecting it to the spur. If everything looks good, put it back on the car and set the gear mesh. If it still doesn't stay in one spot, then put loctite. Don't get too hasty and put superglue the moment it doesn't work. I had the EXACT same problem as you, and after I installed a new pinion, it hasn't fallen off since!

  16. #16
    RC Turnbuckle Jr. kdvanb's Avatar
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    Quote Originally Posted by TraxxasTuesdays View Post
    You could be on to something. It's the stock Traxxas pinion. I've tried probably 8 different grub screws from 3 different brands but that wouldn't make a difference if the threads are bad right before the screw hits the shaft.


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  17. #17
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    hello all....first time post, long time reader. i had the same pinion trouble, and what had happened was the loctite had bonded to the grub screw and wouldn't allow the grub to thread in all the way. i just ran the grub all the way through the pinion to clean off the excessive loctite and haven't had any trouble since.

  18. #18
    RC Turnbuckle Jr. El Sob's Avatar
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    Quote Originally Posted by pct2003 View Post
    hello all....first time post, long time reader. i had the same pinion trouble, and what had happened was the loctite had bonded to the grub screw and wouldn't allow the grub to thread in all the way. i just ran the grub all the way through the pinion to clean off the excessive loctite and haven't had any trouble since.
    Hello, I would like to welcome you to the forum and the addiction! I am glad you found a way to fix your problem. Hopefully it will aslo resolve Traxxas Tuesday's also!
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  19. #19
    RC Racer
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    u are setting the grub screw to grab the flat part on the shaft right ?
    Slash 4x4 MM2 2400kv

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