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  1. #1
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    Unhappy Problems After Spur Gear Melted-Right Rear Tire Rolls Fwd While Left Rolls Backwards!

    I'll start with this is my first RC nitro car/post and I'm super bummed out right now. After running my car (2.5) for literally the 5th time after break-in it's out of commission. I noticed the car not responding to throttle yesterday so I got off the gas and went and noticed something was smoking which I later learned was the spur gear. I proceeded to replace the 70 spur gear that came on the model with the replacement 72 that was included with the original purchase. Everything went on fine, tightened the spur gear nut tight and then backed off 1/4 to 1/2 turn.

    I rolled the rear right tire forward and the left rear tire rolled backwards!?!

    I'm not even going to start it up and try to run it again until I can get this fixed. The spur gear rolls along with the clutch bell like I would think it should. Any ideas on how to fix this or what is wrong would be greatly appreciated for this greenhorn.

    Thanks!

  2. #2
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    That is correct for the wheels to spin in opposite directions. That's how the diff works. If you spin the spur than both wheels will spin the same direction. Welcome and have patience. Any problems just ask.

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  3. #3
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    Nothing to worry about. Thats how it should be. If you had a real car up on jacks and turned a drive wheel, it would act the same way. I would tighten the spur a little, 1/2 turn out is a little too loose. I'd go about 1/4 - 1/8 turn out from fully tight. Good luck and come on by when you have troubles.
    Shaggy...

  4. #4
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    Ok, spun the spur both ways and neither of the tires rolled forward or back. The spur was a little hard to push manually but I think that is normal. The clutch bell and the spur seem like they are lined up and working correctly. After starting the engine I gave it a little throttle and the spur was moving but the car was going nowhere, gave it a lot more throttle and still nothing.

  5. #5
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    Sounds like the idler gear in the tranny.

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  6. #6
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    Ok, I found the idler in the Transmission assembly diagram, 4196. Is removing the transmission and disassembling it something that anyone can do? Will it be obvious as to what is wrong if I open up the tranny?

    I don't want to get into it and not be able to get everything back together. I'd hate for this invested to turn into a brick because I'm in over my head.

  7. #7
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    You will figure it out. Its not that hard. Just pull the tranny out and take a look. Good luck
    Shaggy...

  8. #8
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    The good thing about the rusty is its easy to work on. The tranny is not going to give you any problems. Just work on a clean table and lay every thing out nice and clean.

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  9. #9
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    The tranny is very simple. When you pull it apart, if the teeth on all 3 gears look fine, its probably the gears inside the diff. When your taking the tranny out, check out the drive yokes. If there loose, the diff outputs can spin inside the yokes. Good luck
    Shaggy...

  10. #10
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    Ok, I think I'm going to tear apart the tranny tonight and hopefully find out what is wrong. The thing I'm most concerned about it is getting the stupid thing back together but I guess that's what the exploded views are for. I need to get some grease before I start thought and I don't have a LHS within 90 miles so I think I'll try the bike shop. Looks like Silicone grease and white lithium is what I'm looking for.

    Ok, worst case scenario is I get it taken apart can't find what is wrong and then can't put it back together. Do LHS's work on these for an hrly rate or should I post an ad on Craigslist to find the kid down the street? (I used to work on bikes so I think I can handle this)

  11. #11
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    Stop at home depot or lows and ask for Dow 55 grease. It will do the trick and will be allot cheaper than going to your lhs. They way I look at it, if you can put a crank in a bike, you can handle the tranny lol. At first, I think its harder to get the tranny out than to take apart and put the tranny back together. You shouldn't have any problems. Its a simple truck. Good luck
    Shaggy...

  12. #12
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    Quote Originally Posted by Shaggy101086 View Post
    Stop at home depot or lows and ask for Dow 55 grease. It will do the trick and will be allot cheaper than going to your lhs. They way I look at it, if you can put a crank in a bike, you can handle the tranny lol. At first, I think its harder to get the tranny out than to take apart and put the tranny back together. You shouldn't have any problems. Its a simple truck. Good luck
    Thanks for the confidence Shaggy!

  13. #13
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    When your done with the tranny let us know how easy you found it to be. If the idler is wasted there is a sweet mod for that. But I don't want to throw anything at you that you may not understand. Good luck wrenching.

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  14. #14
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    I have the tranny removed and when I turn the slipper shaft both half shafts turn forward like you would expect. This makes me think the tranny is fine and that I had the spur gear installed wrong. Any thoughts?
    Last edited by knockando; 01-10-2012 at 09:50 PM.

  15. #15
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    You talking about the ball that just pushes onto the carb ? Just pop it off.

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  16. #16
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    Everything in the tranny was completely fine. I think the problem may be the friction pegs. I re-used the old ones after the first spur gear was melted and warped and I don't think they have enough length on them to properly engage the spur gear. Does this sound legit?

    And yes, removing the transmission and tearing it down is very easy.

  17. #17
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    That could be the case. Or the slipper was way too loose. Did you take the diff apart and look inside it?
    Shaggy...

  18. #18
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    A good learning experience !

    Sent from my workbench
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  19. #19
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    Yeah it took me 3 or 4 spur gears to get it right when I first got the trucks lol. Nitro has a real good point there. Once you got the new pegs in there, you shouldn't have any problems with the spurs. You should get at least few gallons of a stock spur if its set right. If its too tight, you can strip the gear or something inside the tranny. Too loose and you can melt the spur and the pegs. After you drive the truck a little more you will know how the truck should sound. You will know when she is revving too high for how fast shes going. If that happens check the spur right away. You will be able to tighten it up before any damage is done. I tighten mine all the way and go back out about 1/8 turn out. I think the manuel calls for 1/4 turn out but where i have a 3.3, I like it a little tighter to prevent it from slipping as much. Good luck
    Shaggy...

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