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  1. #1

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    Redcat Sumo bad sounds no movement

    Hello everyone, I am new to this forum and quite new to RC as a whole. About five years ago I had an HPI nitro truck but only took it out a dozen times or so. Recently I purchase a Redcat Sumo to mess around with in the house... Out of the box it worked very well (minus not being able to adjust the steering yet) but on just my third time running it I got it hung up on the dog pillow and I could instanly hear it missing or making a clicking sound. After checking it out a little bit I decided to pull the motor and check the gear... Sure thing, the gear on the motor was missing teeth. I replaced this gear with one of the others the car came with and it ran great but I would randomly hear it making that same clicking noise. So I removed the motor again and re-installed it trying to ensure that the teeth were meshing but the same issue occurred. Today I ran it for a couple of minutes and out of no where it will not move at all. The motor is going but all you hear is a grinding type of noise that almost sounds like you are sticking someting into fan blades. If I pick the car up, the tires will spin but once the car is on the ground it goes back to making that horrible noise. I havent taken the motor out again yet but I am guessing the gears are all shot but I have no idea where to start. Any help or suggestions would be greatly appreciated as I have no real experience dis-assembling or re-assmbling. Thanks in advance.

    JJ

  2. #2

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    RE: Redcat Sumo bad sounds no movement

    First of all, get ready to get some experience disassembling and reassembling. If you are really paranoid about messing something up get a box with dividers, be organized, and take lots of pictures.
    Second, What kind of sumo do you have?

    For what I'm about to explain I am assuming the truggy or buggy.

    I don't know much about the sumos, but looking at the exploded view from the manual they look similar to larger scales. I would take it apart and check the pinion and spur gears first. The pinion gear is connected to the motor and and spur is the gear it touches. After that there appears to be a shaft that goes through the center of the spur gear with smaller gears connected to the ends? Check that assembly. If neither of those are the problem, I fear that you have stripped one or both of your diffs. The diffs are the gear assemblys that connect to the shaft described above and deliver power in the direction of the wheels. The diffs are located between each set of wheels with shafts going to each individual wheel. Check to make sure the drive cups that connect to these shafts are not stripped somehow before checking the diff. The diffs are secured in a housing that will need to be removed to reach the main gear which can be disassembled by removing four screws on the gear to reach four small umbrella shaped gears.

    I think I covered every possiblity but hopefully someone with one of these will chime in.

    Sumo Gear package part # is 24017.
    Sumo Diff assembly part # is 24020.
    I think the gear package has enough to rebuild one diff and some extras.

    Associated Rc8, Redcat Earthquake 8e, Losi Mini-t, Traxxas: Jato, Slash, TCP, and E-Maxx

  3. #3

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    RE: Redcat Sumo bad sounds no movement

    Yes, check the rear diff, it drives the front diff. The ring gear is plastic. Very easy to remove. Disconnect the top of the shocks from the shock tower. Unscrew the top of the diff case. The diff gears will lift right out from here. The replacement gears are inexpensive for the compete set.
    SELLING MONSOON XTR WITH UPGRADED AND LOTS OF SPARE PARTS - PM FOR DETAILS
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  4. #4
    nitrosportsandrunner's Avatar
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    RE: Redcat Sumo bad sounds no movement

    ORIGINAL: Dads like rc too

    Yes, check the rear diff, it drives the front diff. The ring gear is plastic. Very easy to remove. Disconnect the top of the shocks from the shock tower. Unscrew the top of the diff case. The diff gears will lift right out from here. The replacement gears are inexpensive for the compete set.
    rear diff would not stop the truck from moving while on the ground, as the front diff would still get power and move the truck.

    Im guessing you either have a sumo truck/truggy with a stripped spur gear (the one the pinion turns)

    If you have the truck/truggy, you likely need this:
    http://www.redcatracing.com/s.nl/it.A/id.2778/.f
    SC10rs, 1/6 hummer crawler, Kyosho Twin Force, Lunchbox project, Techone P51,

  5. #5

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    RE: Redcat Sumo bad sounds no movement


    ORIGINAL: nitrosportsandrunner

    rear diff would not stop the truck from moving while on the ground, as the front diff would still get power and move the truck.

    Im guessing you either have a sumo truck/truggy with a stripped spur gear (the one the pinion turns)

    If you have the truck/truggy, you likely need this:
    http://www.redcatracing.com/s.nl/it.A/id.2778/.f
    I thought the motor pinion turned the rear ring gear in the rear diff, which was related to the front diff through a single center shaft. At least that's what I remember from my sumo truggy.
    SELLING MONSOON XTR WITH UPGRADED AND LOTS OF SPARE PARTS - PM FOR DETAILS
    Caldera 10e : Volcano EPX : Monsoon XTR : Sumo x2 :

  6. #6
    nitrosportsandrunner's Avatar
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    RE: Redcat Sumo bad sounds no movement


    ORIGINAL: Dads like rc too


    ORIGINAL: nitrosportsandrunner

    rear diff would not stop the truck from moving while on the ground, as the front diff would still get power and move the truck.

    Im guessing you either have a sumo truck/truggy with a stripped spur gear (the one the pinion turns)

    If you have the truck/truggy, you likely need this:
    http://www.redcatracing.com/s.nl/it.A/id.2778/.f
    I thought the motor pinion turned the rear ring gear in the rear diff, which was related to the front diff through a single center shaft. At least that's what I remember from my sumo truggy.
    I never completely torn down my sumo....
    but going by the exploded view on the manual, it looks like the spur gear has the pinion gear for the rear diff built into it.
    At any rate, part # 24017 has the spur gear as well as the main gears of a diff. so either way, that part # should have the parts needed to get his sumo up and running again.

    SC10rs, 1/6 hummer crawler, Kyosho Twin Force, Lunchbox project, Techone P51,

  7. #7

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    RE: Redcat Sumo bad sounds no movement


    ORIGINAL: nitrosportsandrunner

    but going by the exploded view on the manual, it looks like the spur gear has the pinion gear for the rear diff built into it.


    This sounds right.

    james.jaros, did you ever figure it out?

    Associated Rc8, Redcat Earthquake 8e, Losi Mini-t, Traxxas: Jato, Slash, TCP, and E-Maxx

  8. #8

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    RE: Redcat Sumo bad sounds no movement

    Hey guys, thanks for the awesome responses. Ihave not had a chance to look into any of it yet, unfortunately the day after posting I had to head out of town for a few days. This is also why I havent responded sooner... I will be back home on Tuesday and will start taking stuff apart and will absolutely use a bin with dividers and pics as suggested. Thanks again guys, I will let you know how it goes. Oh, I have the Truggy version of the Sumo.

    James
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  9. #9

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    RE: Redcat Sumo bad sounds no movement

    So I finally got the time to tear it apart today, I am a little confused about the results.

    First the motor pinion and spur gears both seem to be in perfect working condition.

    So then I opened up the rear differential and pulled it out.  Sitting in a free state I twisted one of the diff. outdrives and I noticed that it had free movement for about three quarters away around and then it had quite a bit of resistance for the last little bit.  So, I disassembled this and broke it down to where I could see all of the internal gears.  Once open with the four small bevel gears still installed I again spun the diff. outdrive and noticed again three quarters of a turn was fine, then when I felt the resistance it actually lifted one of the small bevel gears out a little bit.  But the interesting thing was that I didnt see anything wrong with any of the gears at all while I spun it. 

    Now since I am a newbie, should the differential spin freely I am assuming?

    After I re-assembled the back end (to not loose components) I started disassembling the front end...  Again there was no issue with the drive pinion gear that was visible so I removed the differential.  Now this one when spun I could feel resistance the whole way almost like the gears werent meshing properly.  So I again pulled it apart but unfortunately I didnt see anything wrong with the internal gears.  I re-assembled it and  same issue, no free movement there was resistance the whole way. 

    Any ideas?

  10. #10
    nitrosportsandrunner's Avatar
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    RE: Redcat Sumo bad sounds no movement

    I dont think the problem is in the diffs....if it were, you would still have front or rear drive with the model on the ground. Its very unlikely that you damaged both diffs at the same time.

    for your model not to move while on the ground, the problem should be between the motor and center shaft. something there is preventing the transfer of power to the diffs. Again, if the problem was in a diff....it would have to be both diffs at the same time.
    If the problem is in the motor, spur gear or center drive shaft then neither diff will spin with the model on the ground.
    How does the spur gear seat onto the center shaft?
    I assum the pinion gears simply push fit onto the center shaft and have a flat spot so that they rotate on it. But im wondering if the spur gear is slipping on the center drive shaft.

    a diff will sometimes not rotate freely with the case open. and a diff can FEEL hard to turn if turning it by the outdrive. turning it by the wheel it will feel much easier as it takes less force due to the larger diameter of what you are turning.
    SC10rs, 1/6 hummer crawler, Kyosho Twin Force, Lunchbox project, Techone P51,

  11. #11

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    RE: Redcat Sumo bad sounds no movement

    I did check that the spur gear was in tight and I was trying to apply light pressure while spinning it to see if it would slip but I couldnt get it to.  What is also interesting though is that after I disassembled and re-assembled both the front and rear ends, the car actually drives again.  I only got it up and going at about a quarter throttle but it actually moved.  The bad this is that I could hear that same clicking that eventually lead to a grinding type of sound and no care movement in the first place.  It actually also appeared on the rear diff as if it were bent somehow.  It just didnt look the same as the other.

  12. #12

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    RE: Redcat Sumo bad sounds no movement



    Today I completely disassembled again and the only thing I see with a potential issue is the diffs.  It doesnt make any sense based on the info you provided but I am confused and dont really see anything else.  I am tempted to spend the $16 for both diffs and see if it helps.  What do you think?

    JJ



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