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  1. #1
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    Question T-Maxx 4910 pro .15 engine to trx 3.3 engine upgrade help

    Hello,

    I hope I posted this in the proper area of the forum. I have an old T-Maxx 4910 Pro .15 model that I pulled out of the closet and decided to upgrade. I added a TRX 3.3 engine and found that the throttle linkage doesn't connect properly to the 3.3. I found online that there are a few upgrade/conversion units that might work. I would like to know if anyone would know which parts or upgrade/conversion I will need to run the truck. I found a .15 to 2.5 upgrade/conversion and a 2.5 to 3.3 upgrade/conversion. I'm guessing I would need the 2.5 to 3.3 but I don't know if I will need anything from the .15 to 2.5.

    Thanks to anyone who could help.

  2. #2
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    You'll probably have better luck with this question in the T-Maxx sub-forum; I'll move this thread there for you.
    "Happiness depends upon ourselves." -Aristotle

  3. #3
    Marshal Double G's Avatar
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    The .15 is a rotary carb whereas the 2.5/3.3 are slide. The footprint of the 2.5 and 3.3 are the same so if you haven't converted to the 2.5 you could. Just be advised that with the additional power you will start to take out other drive train parts and need replacement.
    The Super Derecho

  4. #4
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    Just be advised that with the additional power you will start to take out other drive train parts and need replacement.
    Hehe, be prepared to upgrade diffs and driveshafts. Stripped my rear diff gear on my 2.5 and still don't know which diffs to replace it with.

  5. #5
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    Diffs for a T-Maxx 3.3 mayhaps?

  6. #6
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    Just thinking out loud here...to go from a Pro .15 to a 3.3, wouldn't he need aspects of both the 2.5 and 3.3 conversion kit?

    First thing he would need is throttle linkage and bellcrank for 2.5/3.3 (which I think are the same, correct me if I'm wrong), basically everything between the servo horn and throttle slide.

    Motor mount: I'm pretty sure they are the same from Pro .15 through 3.3. I had to get a motor mount for my Pro .15 Maxx and got one that was listed as for 2.5 and 3.3. There are some different part numbers out there but I'm not sure what the difference is.

    Then there is exhaust. If I'm not mistaken, the exhaust configuration as far as how it is laid out is the same between the 2.5 and 3.3 Maxx? Meaning, both are right side dump forward of the engine. I'm not sure if the exhaust itself would be different, as in how the header fits the exhaust flange. I don't know if they are the same between the 2.5 and 3.3.

    Kinda seems like the only real difference between the 2.5 and 3.3 Maxx might be exhaust?

  7. #7
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    Thank You, I didn't know where to put the question. Forums can sometimes be perplexing for me since every website is different.

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    Then there is exhaust. If I'm not mistaken, the exhaust configuration as far as how it is laid out is the same between the 2.5 and 3.3 Maxx? Meaning, both are right side dump forward of the engine. I'm not sure if the exhaust itself would be different, as in how the header fits the exhaust flange. I don't know if they are the same between the 2.5 and 3.3.
    Looking at the exploded views it looks like the exhaust is identical, except that the 3.3 comes with the aluminum pipe out of the box. That doesn't really have a significant impact on how everything fits together though.

    2.5 Exploded: https://traxxas.com/explodedviews/T-...ssion-Assembly
    3.3 Exploded: https://traxxas.com/explodedviews/T-...-Exploded-View

  9. #9
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    Interesting. So really he could do either upgrade kit. Does either kit come with the 2.5/3.3 throttle components? The Pro .15 throttle setup is very different and cannot be made to work with the 2.5 and 3.3

  10. #10
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    Traxxas part #4900 kit instructions. Also works on the 3.3 engine.

  11. #11
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    Thanks everyone for the input, very appreciated. I didn't tear down the carb, is the carb supposed to be pushed out or pulled in by the servo linked to the 3.3 carb (i don't know if there's a spring in the carb)?. In the exploded views the 2.5 and 3.3 seem to have the same setup so I will go with the Traxxas part #4900 conversion kit (Thank you grizzly03). I'm going to adjust the clutch so it wont accelerate to quickly. I purchased the 3.3 used and removed the head to check the piston and sleeve which looked barely used. I didn't have to clean it much and it came with the easy start attached and an odd exhaust. I will post back here once I received and installed the parts. https://www.ebay.com/itm/Traxxas-3-3...72.m2749.l2649
    Last edited by Scooter2478; 03-20-2019 at 11:43 PM.

  12. #12
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    Good deal. Odd exhaust likely just means it came off a different model truck or car

  13. #13
    Marshal Double G's Avatar
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    Be very cautious when buying used nitro engines as everyone has "taken care of them," "adult owned," "less than one gallon of nitro," & "properly broken in to a 'T'."

    It is a very dirty engine, has had some unknown pipe with a makeshift coupler held on by standard hose clamps. Plus the air filter is black and the engine itself is not much cleaner. As long as the sleeve isn't scored and it holds compression then it may be alright. Pricey though for what it is - you could have gotten a new one for ~$20 more and not had to worry about the bearings or internals.
    The Super Derecho

  14. #14
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    Jeeze I didn't even see the link. Just checked it out, sound advice as always Double G. That's an odd silencer for sure. But the header and overall layout looks to be for a Maxx application.

  15. #15
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    Be very cautious when buying used nitro engines as everyone has "taken care of them," "adult owned," "less than one gallon of nitro," & "properly broken in to a 'T'."
    Yeah, I'm fine with used engines, but you better get it for like half price if it's used, because you never know what the previous owner did to it.

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