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  1. #1
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    Cause of stripped pinion gear

    Hey on my Maxx I've somehow stripped the rear pinion gear, 8977, on the far end of the center diff, the Pinon that drives the rear diff. What could cause this?
    I'm running 4S, proline trencher 3.8,and I lowered the gearing a little due to the larger wheels.
    Do I need to lower the gearing more? Or is this some part that just wears out?
    Thanks!

  2. #2
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    I should add, so the factory Maxx gearing is 24 / 50 for 140mm diameter tires. The proline trenchers are 170mm diameter. So I calculated new gearing to be 20 / 50, which gave me almost the exact same ratio.
    I calculated — Diameter * pi / (spur / pinion) — and got very nearly the same ratio. So I think that my gearing should be the same, so I’m not over stressing the driveline with the larger tires.

  3. #3
    RC Champion RazorRC22's Avatar
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    Center diff oil is too thick and puts a lot of stress on the spur. Also, are you running on a high traction surface such as the street? That would also do it if you're mashing/landing on full throttle a lot.
    youtube.com/c/RazorRCvideos

  4. #4
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    Quote Originally Posted by RazorRC22 View Post
    Center diff oil is too thick and puts a lot of stress on the spur. Also, are you running on a high traction surface such as the street? That would also do it if you're mashing/landing on full throttle a lot.
    quick question. i watched your video on changing the oil in the center diff.. what oil did you use to thin it out? or what would you suggest since i plan on doing the same.

  5. #5
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    Makes sense! With the stock center diff oil, the car pulls wheelies constantly. The wheelies are fun for my dog who chases the Max, but blows for performance. Looking forward to going with a lighter oil

  6. #6
    RC Champion RazorRC22's Avatar
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    Quote Originally Posted by Furfmonkey View Post
    quick question. i watched your video on changing the oil in the center diff.. what oil did you use to thin it out? or what would you suggest since i plan on doing the same.
    I just used 1k diff oil, I forget which brand, probably Team Associated.

    Quote Originally Posted by dimsdale View Post
    Makes sense! With the stock center diff oil, the car pulls wheelies constantly. The wheelies are fun for my dog who chases the Max, but blows for performance. Looking forward to going with a lighter oil
    Yeah, there is zero give in the drivetrain. I also saw that you switched to steel driveshafts, that again is going to take out all the give in the drivetrain, so something will want to break instead.
    Last edited by Double G; 01-27-2020 at 08:55 AM. Reason: merge, use the "+ if you want to quote multiple posts
    youtube.com/c/RazorRCvideos

  7. #7
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    Quote Originally Posted by Furfmonkey View Post
    quick question. i watched your video on changing the oil in the center diff.. what oil did you use to thin it out? or what would you suggest since i plan on doing the same.
    I went with 50k in the center diff, but you could go up quite a bit based on how hard the stock Fluid was.. anything would be better..

  8. #8
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    Does anyone know what the stock diff oil is? I'm not saying you're wrong Razor .. but 1k seems kind of thin .. like too thin. One of my other vehicles had 10k/100k/10k and I just moved it to 30k/500k/50k for a better response as it was a little too squirrely.

    The Xmaxx is 20mil on the center. Can't seem to find what the Maxx has or what f/r are but based on others I've seen, it would be 1/10 of the center. If the center is 1mil, the f/r would be 100k. Going to 1k is a big jump.
    Last edited by TraxxasTigger; 01-26-2020 at 11:57 PM.

  9. #9
    RC Champion RazorRC22's Avatar
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    Stock center diff is same as Xmaxx -- 20M. If you watched my video, I took out half of it (it was just balled up) and replaced it with 1k. So theoretically 10M. It's not really 10M, but whatever. I would guess it's about 100k in feel.

    I'm not going to get into the rest of the tuning stuff as I don't really agree with what people are doing but that's what I did for the center.
    youtube.com/c/RazorRCvideos

  10. #10
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    Quote Originally Posted by RazorRC22 View Post
    Stock center diff is same as Xmaxx -- 20M. If you watched my video, I took out half of it (it was just balled up) and replaced it with 1k. So theoretically 10M. It's not really 10M, but whatever. I would guess it's about 100k in feel.

    I'm not going to get into the rest of the tuning stuff as I don't really agree with what people are doing but that's what I did for the center.
    thanks for the center diff tip. I want to know your opinion on switching to steel driveshafts after the widemaxx kit.. do you mean i should keep the stock plastic ones because if i switch to steel it will cause breakages elsewhere? i value your opinion and also don't want to damage my new truck

  11. #11
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    Quote Originally Posted by RazorRC22 View Post
    Stock center diff is same as Xmaxx -- 20M. If you watched my video, I took out half of it (it was just balled up) and replaced it with 1k. So theoretically 10M. It's not really 10M, but whatever. I would guess it's about 100k in feel.

    I'm not going to get into the rest of the tuning stuff as I don't really agree with what people are doing but that's what I did for the center.
    That makes a little more sense.

    Quote Originally Posted by Furfmonkey View Post
    ... switching to steel driveshafts after the widemaxx kit.. do you mean i should keep the stock plastic ones because if i switch to steel it will cause breakages elsewhere?
    That is exactly what he means. When you make something stronger, then the next weakest piece breaks.
    Last edited by Double G; 01-29-2020 at 08:43 AM.

  12. #12
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    Tore down my Maxx center diff today. Cleaned it all out with degreaser, reassembled with Team Associated 500k. Will see how this goes. At least now I know what the heck is in there, given that the traxxas “20M” doesn’t even make sense. Now that I know its TA 500k, so if I want to go lighter I know what am getting.

  13. #13
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    Quote Originally Posted by dimsdale View Post
    Tore down my Maxx center diff today. Cleaned it all out with degreaser, reassembled with Team Associated 500k. Will see how this goes. At least now I know what the heck is in there, given that the traxxas “20M” doesn’t even make sense. Now that I know its TA 500k, so if I want to go lighter I know what am getting.
    It's 20 million 'cst' .. or 39x what you put in. TA also makes 20M (million) - as do many others.
    Last edited by TraxxasTigger; 01-28-2020 at 09:53 PM.

  14. #14
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    Quote Originally Posted by TraxxasTigger View Post
    It's 20 million 'cst' .. or 39x what you put in. TA also makes 20M (million) - as do many others.
    Just don’t know that I believe that there really is “20M”. Team Associated goes only up to 1M I think? I tend to think that the “20M” isn’t a real quantitative value - that it’s just some marketing speak for “this stuff is so think it will lock the diff, kthxbye”

  15. #15
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    Using a simple search, Traxxas and Gravity RC make it. Considering TA doesn't have a 1/5/6 scale basher, they may not need that high of a cst rating. 500k is pretty tough. 20 mil must be like concrete .. and essentially completely locks the center diff.
    Last edited by TraxxasTigger; 01-29-2020 at 03:52 PM.

  16. #16
    RC Champion RazorRC22's Avatar
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    For the steel driveshafts, I wouldn't mind running them, but yes something has to give, weakest link is usually the spur gear or driveshafts. Putting in thinner fluid in the center diff should help as some of the power is able to bleed off to the other wheels rather than try to grenade your drivetrain.
    youtube.com/c/RazorRCvideos

  17. #17
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    Quote Originally Posted by RazorRC22 View Post
    For the steel driveshafts, I wouldn't mind running them, but yes something has to give, weakest link is usually the spur gear or driveshafts. Putting in thinner fluid in the center diff should help as some of the power is able to bleed off to the other wheels rather than try to grenade your drivetrain.
    Yep. So (with the steel driveshafts I have) I swapped out the center diff for 500k TA diff oil, and replaced the pinion and spur gear. Drove it not that much bc was using Kraton 6S. Took apart the drivetrain today to see how it was doing and found that the rear pinion was already getting nicked up.

    So I thinned out the center diff fluid a little while I was in there. Took out most of the 500k that was in there and replaced that with 100k. But I noticed that the center diff behaves massively differently depending on how tight the 4 screws are in there. If they are overtight by even a small margin, the diff will get crunchy or “clicky”. So I’m not tightening them more than absolutely necessary.

    Ordering some more pinion. When the current one finally strips out I’ll replace it and go even lighter on the center diff. That is I’ll completely strip clean the center diff and go with TA 100k and not more than necessary.

  18. #18
    RC Champion RazorRC22's Avatar
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    Quote Originally Posted by dimsdale View Post
    Yep. So (with the steel driveshafts I have) I swapped out the center diff for 500k TA diff oil, and replaced the pinion and spur gear. Drove it not that much bc was using Kraton 6S. Took apart the drivetrain today to see how it was doing and found that the rear pinion was already getting nicked up.

    So I thinned out the center diff fluid a little while I was in there. Took out most of the 500k that was in there and replaced that with 100k. But I noticed that the center diff behaves massively differently depending on how tight the 4 screws are in there. If they are overtight by even a small margin, the diff will get crunchy or “clicky”. So I’m not tightening them more than absolutely necessary.

    Ordering some more pinion. When the current one finally strips out I’ll replace it and go even lighter on the center diff. That is I’ll completely strip clean the center diff and go with TA 100k and not more than necessary.

    If your diff is crunchy, your teeth are not meshed properly with the internal gears and will break. Check out my Piranha gear diff video to see how to get it properly aligned and it will spin smoothly. Go to 9:10 --

    youtube.com/c/RazorRCvideos

  19. #19
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    Just to clarify, when I hold one end of the center diff in a vise and turn the main gear with my hand, it is a little clicky. But when I have one shaft end of diff in vise and turn the far end shaft by putting a screwdriver in the pin hole, it's completely smooth. I took it apart and assembled using the method above, which made sense.
    Normal to have that clicky feeling just when turning the main gear?

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