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  1. #1
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    Question Rustler 4x4 VXL - Front differential oscillating noise?

    Ever since I took my Rustler 4x4 VXL for a spin for the first time out of the box, I noticed something of a noise that picked up frequency with speed. Perfectly normal I'd assume with a brushless motor. But the difference is an off-pitch sound (too much stress in gear mesh??) that I've been able to isolate to the front differential. What I'm not sure is if it's from the main ring, sun, or planet gears.

    Is this something I should be concerned about? From what I can tell, it's not effecting performance, and it's not loud or grinding. But like I said, there's definitely something off putting about an oscillating sinusoidal sound.

  2. #2
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    Does it sound like a clicking noise? And are you sure that it is in the front diff? If i were you just open up the pinion/spur gear compartement and see if they are meshed correctly. If they are then remove the motor and roll the car. If the noise stops, it is either your gear mesh or your motor. If it does not, it is most likely in one of the diffs.

  3. #3
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    My initial thought was that it too was the pinion/spur. So I removed the top gear cover and checked the play (spacing) between all teeth. I rotated manually, wiggled back and forth, and proceeded to the next tooth. From what I can tell, it's all good like it's supposed to be.

    To confirm, I'll have to take the front end off and roll it manually.

  4. #4
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    yeah. Be careful though. There is a little plastic piece on the front that is supposed to go into the chassis. I discovered this the hard way when I replaced my servo with a high torque metal one then found out i re assembled it wrong. So just be careful. Also in my experience it did take some force to push the front section on. Good luck! (and I hope traxxas will help you)

  5. #5
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    So I removed the front end and rolled it. It's more than just a noise, there's also corresponding resistance with it. Based on where it's happening in revolution, I'm 99% sure it's occurring with the ring gear. Either it was warped from factory, or the teeth not cut right. Could be some burr too. If so, I might be able to deburr it with a small file; I'll have to take it completely apart for a visual inspection at this point.

    Thing is, I've heard this exact same oscillatory sound with other Rustler 4X4 VXLs on Youtube. I'm thinking it's not just isolated to me. Either a design flaw, or a bad batch in production.

    If it's damaged, I'll contact Traxxas to see what kind of replacement they can do for me. But per the parts list, Traxxas offers a spiral cut version of the same gear. Traxxas Part# 5379R (stock is 5379X). It's a bit pricy though with an MSRP of $45. Worth it??? Less resistances and quieter??

  6. #6
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    In my opinion, no. Quieter, (for me) does not matter. If you want less resistance, upgrade your bearings...

  7. #7
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    What do yo mean upgrade the bearings? They are already sealed ball bearings, what is better then that?

  8. #8
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    They have seals but not 100% sealed so they still get dirty inside.
    The Super Derecho

  9. #9
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    Quote Originally Posted by Pretzell23 View Post
    What do yo mean upgrade the bearings? They are already sealed ball bearings, what is better then that?
    The stock bearings are relatively cheap, though they do function as designed and wanted. If you get ceramic bearings, they might break more, but they will roll much better, and more smooth. They will probably also have better bearing shields. This would make your car more efficient, so that you would not need to spend $45 on a better differential gear...

  10. #10
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    StDragon,

    I just bought a Rustler VXL 4x4 myself, and was wondering the same thing. I have a Stampede VXL 4x4, uses all the same parts in the drivetrain as the Rustler, and it's dead quiet. Let me know what you find out. The rustler is really loud.

    Thanks,

    Rob

  11. #11
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    Upon investigation, rear ring and pinion is really tight. You can feel every tooth when you turn it with axles removed. Front has a hard spot on one side of the ring and pinion. Truck is brand new with only two battery packs run through. Manufacturing tolerances must have a large variance for one to be quiet and loose, and the other loud and tight.

    Rob

  12. #12
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    Quote Originally Posted by rcpepper View Post
    Upon investigation, rear ring and pinion is really tight. You can feel every tooth when you turn it with axles removed. Front has a hard spot on one side of the ring and pinion. Truck is brand new with only two battery packs run through. Manufacturing tolerances must have a large variance for one to be quiet and loose, and the other loud and tight.

    Rob
    Exactly, that was my finding too. I have yet to disassemble the front diff, but there's a hard spot with the ring. Given where it occurs in rotation, it's safe to say it's not the pinion the differential gears. Meaning, isolated to the ring gear.

    If I get time, I'll see if I can take a look-see at what's going on. My suspicion is perhaps the ring gear got warped in manufacturing (uneven tempering process??). It looks stamped and not machined from the pictures I've seen. Anyways, nothing is conclusive until I tear it down.

    If you get around to it before I do, please share your findings.

  13. #13
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    I may take the Stampede apart and compare the parts with the Rustler. All parts are the same part numbers to include the diff cases, completely interchangeable. Then measure the parts and check for differences. I'll let you know.

    Also found out that the Stampede wheelie bar fits the Rustler, so if you want a stiffer, adjustable replacement, parts 6777, 4974, and 4976. If you order the Assembly 4975, you get a part for an EMaxx you don't need that has to be removed and discarded.

    Rob
    Last edited by rcpepper; 03-08-2019 at 02:23 AM.

  14. #14
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    Did some more tinkering. Found the ring and pinion teeth were bottoming out on each other. Took a small file and filed tips of the teeth down slightly. Noise is significantly reduced. Hope this helps.

    Rob

  15. #15
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    Quote Originally Posted by rcpepper View Post
    Did some more tinkering. Found the ring and pinion teeth were bottoming out on each other. Took a small file and filed tips of the teeth down slightly. Noise is significantly reduced. Hope this helps.

    Rob
    Nice! So by chance did it also eliminate the spot causing momentary resistance too?

  16. #16
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    Sorry for the slow reply. The rear is a lot smoother and actually free wheels without abrupt stops unlike before. It would pretty much stop when you let it go. In the front, the hard spot is still there, but much less resistance than before. May tinker with more to see which teeth are causing the problem. But the howling is gone, so may just let it be. Also picked up 2 MPH on my 2S battery from 26 to 28 after the work. That tells you how much it was bound up.

    Rob
    Last edited by rcpepper; 03-19-2019 at 03:05 AM.

  17. #17
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    Quote Originally Posted by rcpepper View Post
    Sorry for the slow reply. The rear is a lot smoother and actually free wheels without abrupt stops unlike before. It would pretty much stop when you let it go. In the front, the hard spot is still there, but much less resistance than before. May tinker with more to see which teeth are causing the problem. But the howling is gone, so may just let it be. Also picked up 2 MPH on my 2S battery from 26 to 28 after the work. That tells you how much it was bound up.

    Rob
    I spent a long long time trying to get my diffs perfect. I ended up emailing traxxas and they told me just to run them. I did, and now they run flawlessly.


    Sent from my iPhone using Tapatalk

  18. #18
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    Quote Originally Posted by ati View Post
    I spent a long long time trying to get my diffs perfect. I ended up emailing traxxas and they told me just to run them. I did, and now they run flawlessly.


    Sent from my iPhone using Tapatalk
    Just so I'm clear...Traxxis suggested to just run it as in wear it down? Approximately How many runs did it take to run flawlessly?

  19. #19
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    My front diff on my rustler 4x4 is stiff. Like, very stiff compared to the rear. The rear will spin freely with little effort and the front is really stiff. It feels like it rolls okay by hand, and I did take the whole front end off and took apart the diff. Nothing is damaged or anything like that. I reassembled the diff and it was still incredibly stiff when I turned it by hand. The rear diff turns very easily in my hands. Should I be concerned?

  20. #20
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    Been running on the pavement (60MPH) at a local school parking lot on the weekends. That front dif ring-gear is still noisy as heck.

    I'm real tempted to just replace it with a cross-cut gear. But pricey As far as upgrades are concerned, priority is GTR shocks and springs first.

  21. #21
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    Traxxis apparently is correct - the problem is now gone after running for awhile now. Guess the tolerances are so tight that a break-in period is required.

    I'm calling this issue "resolved"

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