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  1. #1
    RC poster
    Join Date
    Dec 2012
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    3

    Transmission - Grinding Gears and motor question.

    Hi Everyone,

    I'm new to RC Trucks, but need some help. I bought a Traxxas Slash 2WD Velineon Brushless for my 13 year old son for his birthday last month. He loves the truck and hasn't been driving it beyond what I would consider normal conditions for the truck (yes....some jumping, but in top soil type dirt off small jumps he built with a shovel).

    One day after driving, it started to make a horrible grinding noise from the gears in the transmission. Upon closer inspection, it revealed that he cracked the main frame (grey frame that the battery mounts too and all the rest of the suspension). There was also a crack in the plastic gear box.

    After tearing it all down, all the gears appear fine, so my question is, could the "grinding" gears actually be slipping gears from the gear box case not being tight enough because of the cracks?

    Is it normal for one rear wheel to turn the opposite direction of the other rear wheel when turning it manually by hand? When I removed the motor, it didn't do this, but as soon as I install the motor and re-engage the metal gear on the motor with the bigger plastic gear (slipper clutch?) then it does this.

    I plan to replace the gear box (grey plastic casing around all the gears) and the main grey frame, but while I have the entire transmission apart, are there some typical failure items in there that I should just replace while I'm at it?

    Also, one other question about the motor. I noticed that the main shaft coming out of the motor is not centered. It's like it is off to one side and when you spin it manually, you can see the main shaft spinning in kind of an oval shape rather than being perfectly centered. I assume this isn't right? Are these serviceable or am I just SOL and have to also buy a whole new motor?

    I realize I may not have some of the terminology correct on the parts so I've included some pictures to try and help.

    A view of where the main frame broke:


    Cracked gearbox.






    Notice how the main shaft coming out of the motor is not centered. Not normal....right?

  2. #2
    RC Racer
    Join Date
    Nov 2012
    Location
    San Jose
    Posts
    171
    Are you saying that the shaft coming out of the motor is not straight? If it is moving back and forth while rotating, that will mess up the mesh between the spur and pinion gears.
    You can buy a rebuild kit if this is the case.
    DJ

    Rustler,Slash 4X4, 1/10 Rally

  3. #3
    RC poster
    Join Date
    Dec 2012
    Posts
    3
    Quote Originally Posted by djbrun View Post
    Are you saying that the shaft coming out of the motor is not straight? If it is moving back and forth while rotating, that will mess up the mesh between the spur and pinion gears.
    You can buy a rebuild kit if this is the case.
    Yes, the main shaft coming out of the motor "wobbles" side to side when it is spinning. It is off-centered.

    When I tore everything down, I was expecting to find something wrong with the gears. Aside from the broken chassis and gear box cover, I technically don't see anything wrong with any of the gears so I'm wondering if the motor is the main problem (aside from the need to replace the obvious broken parts).

    Are you saying there is a rebuild kit for the motor, or are you referring to the gears?

    Also, if we have any intention of upgrading to Lipo, are there some necessary parts in the drive train that we should replace?

  4. #4
    RC Champion
    Join Date
    Nov 2011
    Location
    North Central OH
    Posts
    1,050
    There is a $12 motor rebuild kit, part # 3352.

    Two bearings and a bushing. Pop the end cap off on your motor, two plastic tabs that lock over a screw head. Remove exposed side screws. Now you will have to pull hard to extract the rotor because of the powerful magnets inside. Look closely for a tiny shaft spacer bushing, some will have one some won't and it will need to go back on just where it was. There will be another bushing that is also supplied in your rebuild kit. Old style Velineon or new style and I see yours is the new style.

    Also in your trans case on the gear shaft sides you will find teflon washers, make sure these go back on when you reassemble it!

  5. #5
    RC Turnbuckle Jr. billy-bones's Avatar
    Join Date
    Nov 2012
    Location
    Michigan
    Posts
    6,045
    Looks like the bearing went out on the motor, just get the set Kwitty said,no problem.
    And your trans,never saw one broke there,but again,most likely the bearing went out.
    I rebuild,or rnr mine every week after weekend racing.
    Except for the broken trans case,about $12 looks like normal where.
    Quote Originally Posted by Winston View Post
    Hi Everyone,

    I'm new to RC Trucks, but need some help. I bought a Traxxas Slash 2WD Velineon Brushless for my 13 year old son for his birthday last month. He loves the truck and hasn't been driving it beyond what I would consider normal conditions for the truck (yes....some jumping, but in top soil type dirt off small jumps he built with a shovel).

    One day after driving, it started to make a horrible grinding noise from the gears in the transmission. Upon closer inspection, it revealed that he cracked the main frame (grey frame that the battery mounts too and all the rest of the suspension). There was also a crack in the plastic gear box.

    After tearing it all down, all the gears appear fine, so my question is, could the "grinding" gears actually be slipping gears from the gear box case not being tight enough because of the cracks?

    Is it normal for one rear wheel to turn the opposite direction of the other rear wheel when turning it manually by hand? When I removed the motor, it didn't do this, but as soon as I install the motor and re-engage the metal gear on the motor with the bigger plastic gear (slipper clutch?) then it does this.

    I plan to replace the gear box (grey plastic casing around all the gears) and the main grey frame, but while I have the entire transmission apart, are there some typical failure items in there that I should just replace while I'm at it?

    Also, one other question about the motor. I noticed that the main shaft coming out of the motor is not centered. It's like it is off to one side and when you spin it manually, you can see the main shaft spinning in kind of an oval shape rather than being perfectly centered. I assume this isn't right? Are these serviceable or am I just SOL and have to also buy a whole new motor?

    I realize I may not have some of the terminology correct on the parts so I've included some pictures to try and help.

    A view of where the main frame broke:


    Cracked gearbox.






    Notice how the main shaft coming out of the motor is not centered. Not normal....right?
    Built Ford Tuff With Chevy Stuff.

  6. #6
    RC poster
    Join Date
    Dec 2012
    Posts
    3
    Thanks for the replies. I know my questions probably sounded dumb at first, but I figure there is only one way to learn. Now that I've torn into this, I see how it all works and I like the idea of being able to help my son maintain it.

    I pulled the motor apart and it looks pretty obvious. Small ball bearings fell out when I pulled the magnet/drive shaft. The bearing on the side the motor where the shaft exits was totally shot. The problem now is that I'm not sure how to get the remnants of the bearing out. I can see how it would be pretty easy to insert a socket or something in there when the entire bearing is in tact, but I basically just have the outer most race of the bearing so there isn't much to have something butt up against to drive it out. Any ideas?

    So at a minimum it looks I'll need a motor rebuild kit, new chassis, and the gearbox.

  7. #7
    RC Qualifier
    Join Date
    May 2012
    Location
    South Jersey
    Posts
    696
    i have had mine 6+ feet in the air and never done that much damage

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