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  1. #1
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    Exclamation Spur gear not lasting. What to do?

    Hi everyone. So after my old T-Maxx has been sitting on the shelf for years I deciced to get my self a brand new Revo 3.3

    My first problem after the 3rd tank while breaking it in the spur gear striped a section and would not move forward anymore. Kinda annoyed I ordered a new one that was in stock but it was a 36t and not the 38 the Revo came out with.

    Just went out after 2 weeks waiting for it only to just last 2 minutes before shreading this spur gear completly.

    What am I doing wrong? What can I do to stop this from happening if i buy a 3rd one. Should I be upgrading to a metal one instead? Any suggestions will be good.

    Thanks

  2. #2
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    I would get a metal one sounds like your mesh is wrong though


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  3. #3
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    Just remember if there is another underlying issue you havenít found and you replace the plastic spur gear with a metal one, you will be more likely to do more damage to your vehicle. At least with the cheap plastic spur gear you donít have to worry about breaking other parts. I agree with the above post as well, is your mesh set correctly. Iíve used the same spur gear for years. And that is with some heavy use. If you set your mesh correctly you should not have any issue with chewing the spur gear up.

  4. #4
    Marshal Double G's Avatar
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    Oh the typical simple answer of "get a metal one" when that is a band-aid for a broken bone. You are taking the "fuse" per se and moving it to a deeper part of the drive train. A properly squared engine and transmission as well as good mesh will result in a long-lasting plastic spur. Make sure the chassis under the engine is not bent, the engine mount is not bent or cracked, the engine is secured to the mount, the transmission is tight to the chassis and no pads are missing from the slipper clutch. If all is good, then mesh the gears with a piece of paper, tighten the engine mount, recheck and go.

    Proper set-ups will last years and nothing kills a day when the spur strips. In case this ever happens to me I have one on hand which I bought years ago.
    The Super Derecho

  5. #5
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    Well said!!!

  6. #6
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    I’ve ordered another plastic one and going to try and get it set first. Is it common for the mesh not to be set correctly out of the box? I would assume it would have been all set to complete the break in. Haven’t even got to doing jumps yet.

  7. #7
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    Well for one in your first post you state that the spur gear you replaced the one that got chewed up with was not the stock 38t but rather a 36t. You should have had to set the mesh for this one. Not sure if you did, but that would make all the difference. As for the mesh being set out of the box, i would have checked it before running the motor. Even though it is a RTR, it best to go over the entire vehicle and check all the screws, gear meh, shocks for proper oil levels, motor mount screws, and so on. This will prevent a lot of issues.

  8. #8
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    I would give the truck a quick going over. Checking for anything loose. I purchased a Jato over the summer and the slipper was loose and wheel alignment was way off right from the factory. These vehicles are mass produced, so items slipping through quality control can and do happen. Spending the time to do a pre-run check would help prevent problems before they start.

  9. #9
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    I bought my Revo 3.3 about 4 months ago and it also came with a loose slipper from the factory. Also, my gear mesh wasn't set properly and the engine mount positioning screw wasn't tightened down.

    Just a note from my side regarding the 36T and my personal experience (I generally bash at a BMX track and dirt with some grass). If I am not mistaken you would need to get a larger bell crank to mesh the pinion with the spur gear. I had a 36T which I tried fitting and after extending the motor as high as possible the gears still didn't even touch. Currently I am running a 42T Hot Racing spur gear. I also went the extra step and removed the OptiDrive system and doing the forward only conversion with the Robinson Racing steel gear set. doing the entire tranny with metal gears just makes the truck so much more reliable as do sometimes abuse it coming out of jumps.
    Slash 4x4 VXL
    Revo 3.3

  10. #10
    Marshal Double G's Avatar
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    Confused by the term "bell crank." Do you mean clutch bell which is the gear (not a pinion) that houses the engine clutch? What tooth pinion where you trying to run with a 36T spur? You'll need a hardened clutch bell if you are running the HR spur otherwise you'll strip the bell; but my guess is that you have a pretty small bell to fit it. 42T seems quite a bit short as the stock 3.3 runs well with the standard 15T/38T or even 14T/38T. I liked running mine 14/38 with a standard gear ratio inside but now with my .21TM it is happy with the 16/38 and standard ratio.
    The Super Derecho

  11. #11
    RC Champion olds97_lss's Avatar
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    I'm running plastic spurs on both my 21tm revo and my big block revo without issue. I haven't changed a spur on either in years due to stripping, only to change ratio's. I most recently changed my 21Tm revo to a bit lower gearing (standard ratio RRP gears in the trans) to have a bit more torque for bashing at a grass bmx track. Pretty sure I'm running 16/40. I've run half a gallon through it since and no issues. Up to that point, I had 2.5 gallons or so on the other spur (38T) and it's also still fine.

    To me, it just seems like your not setting the mesh right or you have loose screws in the motor mount or a cracked motor mount cradle. The plastic spurs hold up great and give you a week spot that's easier to replace than trans gears or a diff.

    For what it's worth, by the time I got a full gallon through the 21TM, I had to replace the plastic gears in the trans 3 times, then I replaced them with RRP like my big block revo. Kept frying the main input gears or output gears would shear the pins off. Not once did I cook the spur.
    Expert rigging at it's best!

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