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Transmission troubleshooting

Discussion in 'Traxxas T-Maxx' started by caseymou, Jun 18, 2006.

  1. caseymou

    caseymou Well-Known Member

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    I bought a used maxx from ebay that was missing the spur gear. It was advertised as "all it needs is replacement spur to run". I replaced the spur but noticed that when I turn the spur the wheels don't spin. I took the tranny apart and didn't notice any stripped gears either. It looks like there are some centrifigal clutches which would require more rpm than I can provide with my hand spin in order to engage. Is this accurate? Are there checks I can do by hand before starting? I am dealing with engine issues atm so it may be a couple of days before it runs.
     
  2. SMaxxin

    SMaxxin GAME TIME! Staff Member

    A tranny that still has reverse will not spin the tire when you turn the spur gear. The clutch you see inside the tranny is for second gear, it required thousands of rpms before it engages. You didn't see any stripped gears so thats a good thing, start it up and give it a try.

    Good luck!
     
  3. olds97_lss

    olds97_lss Well-Known Member Supporter

    Yeah, with the maxx, there's a jerking motion off the line as the forward or reverse clutch engages inside the trans. Most people replaced their revers with a FOC (forward only conversion). This gets rid of the jerkiness off the line and lessens rotational mass inside the trans since it removes all the reversing junk.
     
  4. speedticket75

    speedticket75 Well-Known Member

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    maybe look for a shear pin on one of the gears in the transy.......dont know if your model has one but mine does
     
  5. kurt_02f150

    kurt_02f150 Gone - bye bye.

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    there is a cross pin. (i dunno how to describe the location) It can snap and definately cause the problem you are having. I think its on the primary drive gear but i'm not sure. hopefully someone can chime in with the right location.
     
  6. NCNitro

    NCNitro Fist of Goodness Staff Member

    A spur gear with the reverse stuff still in the tranny will not move the truck when you turn it by hand. Don't bother with the pin until you actually run it and see if it engages under power. When it takes off the jerking will be normal due to the centrifigal clutch in the tranny. I would definately suggest removing reverse, and adding the foc, it is the best low dough mod for a maxx imo.
     
  7. rehpotsirk

    rehpotsirk Well-Known Member

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    The pin that kurt 02f150 is talking about is the shear pin on the spur gear input shaft. This pin can be replaced by a cut off piece of an allen wrench that is the proper size for a "press fit". After you have been in this hobby, you will have rounded off allen wrenches laying around somewhere. Reading this forum and in others, this pin likes to fall out or even break.
    As for the jerking on minimum throttle, you can do the FOC. If you want to keep reverse like I did, do the following:
    Disassemble the two halves of the tranny. Please do this slowly, patiently, and PAY ATTENTION! There are teflon washers located in various spots on the shafts.Use Traxxas' website on the exploded views for proper assembly.
    While the tranny was apart, I opted to disassemble the second speed gear set. I loctited the set screw that holds the gear to the flat spot on the shaft (this screw has been known to come loose and fall out) AND put paint around the second speed adjustment screw to make it more noticable as noted later in this "article".
    On the bottom set of gears that the shift fork goes around. Those are your output gears sets. Take notice that the forward output gear is blue on the end and has a shiny pawl while the reverse has a black end with a dark pawl. This advice will help in reassembly.
    Take the forward and reverse gears off.
    On the side you will see a pin. Knock this pin out BUT LEAVE THE PAWL, BALL, AND SPRING IN THE GEAR. THIS IS FOR SAFETY REASONS. REMOVING THE PARTS WILL ALLOW THE TRANNY TO BE SHIFTED TO REVERSE AT HIGH SPEEDS CAUSING TOTAL CHAOS AND MEYHEM TO THE TRANNY GEARS.
    Replace the previously removed pin with a driveshaft pin that is used to "lock" the driveshafts to the trans and diffs. Prefer to use the longer ones. i.e. the one that is used for the brake disc hex.
    If the long pin is used, thread in until it is flush with the gear. The other end will stick out of the gear and catch the inside holes in the shifting bell housing.
    If the short pin is used, thread it in as far as possible BUT NOT TOO FAR! Check the movement of the pawl as you thread the pin in. DO NOT LET THE PAWL BIND UP!
    Do the same procedure to the reverse gear if you don't want the "jerkyness" to happen in reverse.
    This mod to the reverse is totally optional!
    I did it to mine. Used a long drive pin in the forward gear and short pin in the reverse gear.
    CAUTION: DOING THE MOD TO THE REVERSE GEAR WILL ALLOW THE MAXX TO SHIFT INTO REVERSE OR FORWARD AT LOW SPEEDS!!!!!!!! Not doing the mod to the reverse gear will still allow the Maxx to be shifted from reverse to forward at low speeds.
    Like I said, I did this mod to mine yesterday since the trans was apart on account that I stripped a reverse output gear. Tried it out just this morning on the pile of dirt (3 ft tall) that I have "accumulated some how" in my driveway. I can now slowly creep and crawl up the pile as before, I had to have some speed going up it.
    Also noticed the abilty to do wheelies was a lot easier now that the tranny is in a fully locked position.
    THIS MOD IS FULLY REVERSABLE!!
    Also if you choose, you do not have to retain the pawls, balls, and springs. THIS GUARANDAMNTEES THAT THE TRANS CAN BE SHIFTED EITHER FORWARD OR REVERSE AT ANY AND ALL TIMES!!!!!!!! Retaining them in the mod will not allow this.
    NOTE: Now the spur gear will turn counterclockwise at all times since either forward OR reverse is "locked" in.
    To adjust the set screw for the second speed shift: stick the allen wrench in the access hole and push the Maxx forward until the second speed set screw is visible. Hench the (red) paint applied earlier in this "article".
     
    Last edited: Jul 16, 2006
  8. rehpotsirk

    rehpotsirk Well-Known Member

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    Small update to this tranny mod. So far it is working wonderfully. I can drive the Maxx slower than I can walk. I have ran into one problem. The tranny has locked in forward twice now and it has been while I have been climbing things at a very slow speed. From what I have read elsewhere, this does happen when all pawls and parts are left. What happens is that the pawl becomes "wedged" against the cross pins in the shift bell and can be cured by doing 1 of 2 things: cutting or drilling the pins out OR not putting the pawls in there to begin with. My Maxx is apart for repairs due to the house's foundation getting in the way of my driving and I plan to re-mod the tranny so that it won't "lock" in forward at least. I haven't decided on what to do. I have a few days until replacement parts show up. I will keep everyone posted.
     
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