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  1. #1
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    Tmaxx starts but wont move

    Just got a tmaxx classic 4910. Was told it has been sitting for awhile. Got it started but would only run at real high rpm. When it did run the tires would spin as soon as I started it. I decided to replace the motor and upgrade to the 3.3. I put motor in and it starts fine when you give little gas it does not move. when I pinch gas line to turn off it goes to a high rpm and tires want to spin then it dies. I gave it some gas when it was running and it just wanted to buck forward. Spur gear moves freely in both directions when motor not running. When running doesn't move in forward or reverse. Spur gear is meshed perfectly on clutch bell. Any help would be greatly appreciated. Thanks

  2. #2
    Marshal Double G's Avatar
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    Spur gear tight enough? If so, do the center shafts spin? If not, you've narrowed the problem to the transmission. Is the shift lever for forward/reverse all the way in or out? It needs to be in order to engage a gear.
    The Super Derecho

  3. #3
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    Spur gear is tightened so the spring is stacked then backed off a little. Not sure by what you mean when you say do the center shafts spin. Thanks in advance.

  4. #4
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    The forward/reverse rod is engaged all the way in. The shafts under the truck that are connected to the trans and diff both move when I turn with my fingers. A little tension as they are moving the wheels as I spin them.

  5. #5
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    when you replaced the engine, did you get a new set of clutch shoes? Traxxas makes 2 different shoes - 4146 and 4146x. the 4146x is used in the 3.3 engines with the larger bells.

    I can imagine that what you are describing is it takes high RPM to throw the smaller shoes out far enough to engage the clutch bell.

    Just a thought

  6. #6
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    No I didn't replace the clutch shoes. Im using the same bell as the motor with the 2.5. Just transferred parts over to it. When I took engine to hobby shop to trade it in they took old motor apart and looked at everything I would be transferring to new motor and said everything was fine.

  7. #7
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    When you give it throttle does the spur gear move at all? You could have an internal trans problem with the pawls for forward and reverse gear. If the clutch engages and the spur spins, then that for sure means you have an internal problem. If you have to rev it up high before the clutch engages, then I would say you have a clutch problem. You can of course just go with a foward only kit, it will perform alot better. Good luck.
    Rusty 2.5R,T-max 2.5 & 3.3,Summit VXL Nitro 4-tec

  8. #8
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    As soon as I start the motor the spur gear moves. Is it suppose to turn all the time or no?

  9. #9
    RC Turnbuckle Jr. Snook Man's Avatar
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    Preferably the spur should not spin at idle speed but it’s not uncommon for it to spin some if the idle is high.
    How much throttle are you applying? You stated it will buck forward when you gave it throttle…And the wheels will spin when you pinch the fuel line. It seems to me that there may be nothing wrong except not enough throttle input to fully engage the clutch in the transmission. The 2.5 with reverse will buck forward until an ample amount of throttle is applied. It’s not a constant drive like the 3.3 version is when it still has reverse installed.
    No slipper/tall gearing/power = broken parts.

  10. #10
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    I would say I gave it almost half throttle. Just seems like a lot to get it to just barely move forward. When I pinched the fuel line and the rpm goes up is when the tires want to go like a raped ape. I messed with the linkage that goes from the servo to the carb. When I did that it wanted to move as soon as it started. I put the linkage back where it was. The old motor (the 2.5) only started on high rpm and tires spun as soon as it started. When I did give it a lot of throttle with the new motor it wanted to die before it would buck or tires moved. Most of the time though only time it wanted to move was when I pinched the line which was weird cause I had it at that rpm with the line not pinched and it didn't move.

  11. #11
    RC Turnbuckle Jr. Snook Man's Avatar
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    Sounds like break-in pains to me. Rich carb settings = low power output. When you pinch the fuel line it leans out the tune and more power is produced at the same rpms than when rich.
    No slipper/tall gearing/power = broken parts.

  12. #12
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    Makes sense. Any suggestions?

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