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  1. #1
    RC poster
    Join Date
    Aug 2018
    Posts
    2

    Tmaxx FOC Install and now only goes in reverse

    I have a classic Tmaxx 2.5 upgraded to the 3.3. I acquired the truck used and have been having a lot of problems getting the truck to run correctly. Finally got it tuned to where it would run, but then found that that one of the gears in the trans was stripped: was at my local hobby store and purchased the FOC kit. Installed and found that the truck is now not forward only but is reverse only. I have searched the internet to find a solution, and have been out of luck. I took the trans assembly back apart and check the install, as per the Traxxas instructions the install was performed correctly. put it back together and the truck did the same thing, reverse only. Someone has to have an idea of what may be going on. I only removed the transmission from the truck, could someone prior to my ownership of the truck have swapped something else that could cause this? What else on the truck could cause it to go in reverse with FOC installed. I only drove the truck for a short period of time in front of my house prior to the disassembly of the trans, and it did drive forward. My best guess is that the truck was driving forward in reverse. Any help will be greatly appreciated. I am new to the hobby so please be kind, we started in the hobby as a result of my son wanting to start, now we are 5 trucks in, and growing. My garage that once built drag bikes has now been almost fully converted to a RC car shop....lol Someone out there has had to run into something similar before, your help is needed.

  2. #2
    RC Racer
    Join Date
    Apr 2017
    Posts
    191
    Your differentials are in backwards, flip them both around and it will go forward

  3. #3
    RC poster
    Join Date
    Aug 2018
    Posts
    2
    just to verify, you are referring to the front and rear diff assemblies? don't mean to sound uneducated, but before I take anything else apart I want to make sure. In my line of work 98% of problems are installer error, I try to stay in the 2%.....lol. Doesn't always work though

  4. #4
    Marshal Double G's Avatar
    Join Date
    May 2008
    Posts
    12,646
    Yes, the front and rear differentials must have been out at some point and reinstalled incorrectly. So to make the truck run right the previous owner had to put the transmission in reverse to make it go forward and forward to make it go in reverse. You need to take them out and flip them over so as you look at it the screws are on the right side.
    The Super Derecho

  5. #5
    RC Turnbuckle Jr. Nitronaught's Avatar
    Join Date
    Oct 2005
    Location
    South Florida
    Posts
    19,466
    Take a look at the exploded views to see which way the differential case screws are facing, best way to tell if your diff is in correctly or not. No matter which diffs you are using the screws are facing the same way. 3.3 or 2.5 diffs.
    Front


    Rear

    All Lives Matter
    United We Stand, Divided We Fall

  6. #6
    RC Champion
    Join Date
    Feb 2013
    Location
    Parker, CO
    Posts
    1,372
    I am pretty sure the diff cases have a marking on them that either says 'up' or an arrow pointing up. But yes, the diffs are installed upside down. Take them out, flip them over in the bulkheads and reinstall.
    I have an RC problem...

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