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  1. #1
    RC Turnbuckle Jr. Snook Man's Avatar
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    T-Maxx 2.5 transmission 3 speed conversion

    Hereís the walk through for the 2.5 T-Maxx transmission 3 speed conversion.

    Itís quite long so I am posting it in 5 parts.

    If you attempt this mod please be careful with the power tools or whatever tools you use and wear your safety glasses.
    I canít be held responsible for any damages you may incur to yourself, the transmission or your Maxx. Higher speeds will result in more damage in the event of a high speed crash.

    Take your time and read it thoroughly. I will be happy to answer any questions you may have.
    No slipper/tall gearing/power = broken parts.

  2. #2
    RC Turnbuckle Jr. Snook Man's Avatar
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    Part 1 Tranny housing modification

    The first thing needed for the 3 speed conversion is modification to the tranny housing.
    If you cannot complete this part the rest is even more difficult.

    The front half of the housing needs to be modified by removing some plastic in the area of the primary forward gear. The addition of primary 3rd gear, hub, clutch and relocation of the primary forward output gear require it.

    I used a 1 and ľ inch forstner bit chuck in a drill press with a jig to hold the case plum and square with the table. A dremel can also be used with a sanding drum, just be careful not to sand all the way through the housing. I removed the plastic to a 16mm depth.
    This needs to be centered with the primary shaft bearing as best as possible as there is little room for error.


    Next you will need to drill two holes in the front half in the area where the forward/reverse shaft would be to install a plug for access to the 3rd gear shift point adjustment.
    The two holes are different sizes for the stock plug, so choose the bit that suites you best depending on the plug you use




    I chose to also use a larger bearing for the primary shaft.6x12x4mm. I enlarged the primary shaft bearing recess to 12mm (in both halves) with a 12mm forstner bit. Be careful to center the bit when making the hole larger. (A jig comes in handy here as well)
    If you have the means to make the needed new primary shaft, it can be cut down to fit the stock 5x11x4 bearing and you can skip this step if you want. (I like larger bearings and itís easier than reducing the size of the primary shaft ends).

    Thatís all the modifications needed to the tranny housing.
    No slipper/tall gearing/power = broken parts.

  3. #3
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    Part 2 Input shaft modification

    Next the input (slipper shaft) needs to be modified with the addition of another gear.
    I chose to use the largest gear I could fit without any modifications to the tranny housing.
    I used a 28T 2.5 T-Maxx forward primary gear.
    The gear hub needs to be cut off; the face of the gear reduced (to clear the housing) and a hole is drilled through the input shaft and gear to attach the gear with the supplied grub screw pin that comes with the forward primary gear.

    Forward primary gear.


    Forward primary gear with hub cut off.


    Hole drilled through input shaft.


    Hole through gear.


    Gear attached to the input shaft. The E-Clip is still needed.



    That completes the input modification.
    No slipper/tall gearing/power = broken parts.

  4. #4
    RC Turnbuckle Jr. Snook Man's Avatar
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    Part 3 Primary shaft modification (1)

    Next are the most difficult parts; the primary shaft and gears.

    A new 6mm primary shaft is needed to add the 3rd gear.
    I used an aluminum shaft to get all my measurements correct and later made a new shaft out of steel.
    The shaft is simple; itís the same length as the original primary shaft and 6mm in diameter.
    The stock 2.5 tranny 1st and 2nd gear hub assemblies including the OWB are used and mounts on the new primary shaft just as it does to the stock shaft. I simply countersunk a hole to lock the 2nd gear clutch to the shaft instead of notching the shaft.


    The parts I used for the primary 3rd gear assembly include;
    1 Ė Tower part # LXKHH2.
    1 Ė Tower part # LXDLG1.
    1 Ė 6x12x4mm bearing.
    3 Ė 2mmx8mm threaded screws and washers.

    The 32T gear hub needs to be shortened; a bearing recess needs to cut into it and the area where the attachment screws to the hub are needs to be widened.
    Not an easy task, but a drill press, dremel, files, and sanding stones will all come in handy.

    Stock 32T gear.


    Gear with hub cut to length and widening of the attachment screw locations.


    Gear with bearing recess cut into it.


    Gear with bearing installed.


    Next the 3rd gear clutch hub needs to be modified to fit the 3rd gear.
    Again, a drill press, dremel and assortment of files can get the job done.




    Stock clutch hub prior to modification.



    Clutch hub after modification. Take off just enough material around the hub to let the hub fit into the recessed area of the 3rd gear.
    My fit was tight enough that I slightly heated the gear and chilled the hub for a perfect fit.


    Attach the hub to the gear with the 3 2mm screws. (Use Loctite).

    3rd gear with hub attached.

    No slipper/tall gearing/power = broken parts.

  5. #5
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    Primary shaft(2)

    The 3rd gear and hub with bearing is then slid onto the primary shaft.
    Be sure to use a Teflon washer between the 3rd gear hub and the OWB.

    3rd gear, hub and bearing on primary shaft.

    Note: a washer/bushing is then needed between the bearing and clutch.

    Install the clutch on the shaft and secure it with the grub screw so that it allows the gear and hub to spin freely on the shaft with a s little play as possible.
    I counter sunk the shaft for the location of the grub screw.

    Once installed, 1st, 2nd and 3rd gears should spin freely on the primary shaft with little play. 1st gear should engage the shaft with the OWB when rotated clockwise (while looking at the 2nd gear clutch hub.

    Next you need a forward output gear. I have always thought the stock FO was a weak point due to its narrow width so I installed a Revo forward only gear. Parts # 5394X.
    I used the primary gear from the set, cut the shoulder to length so it would ride against the tranny housing bearing and drilled the primary shaft to mount the gear with the included grub pin screw.

    Be sure to leave a few millimeters between the forward primary and the 3rd gear clutch and hub so it does not bind.

    That completes the new primary shaft and gear assemblies.
    No slipper/tall gearing/power = broken parts.

  6. #6
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    Part 3 output shaft modification

    Next you will need a 2.5 FOC output shaft and gear.
    This is pretty straight forward. All thatís needed is to remove the gear from the shaft.
    Flip the gear over; orient it on the shaft so it meshes with the new forward primary gear.
    Drill a new hole in the shaft and remount the gear.

    FOC shaft with new hole location.


    FOC shaft with gear mounted/flipped in new location.


    That completes the FOC output shaft and gear.
    No slipper/tall gearing/power = broken parts.

  7. #7
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    Part 5 assembly

    The rest is simply installing the shaft and gear in the housing.

    Input shaft installed.


    Primary shaft installed. Slightly raise the input shaft while installing the primary.


    Output FOC shaft installed.


    Tranny halves matched together completes the conversion.


    Image of mesh between the primary forward output and the FOC output gears.
    Much beefier than the stock forward primary.


    3rd gear shift point adjustment is much easier than you would think with the tranny installed. The only difficult part is the access plug is located where the stock battery box would be and it or the fuel tank that may have taken its place needs to be removed for access.



    Thatís it! 3 gears and a stronger forward primary.

    Hope you enjoy.

    Snook.
    No slipper/tall gearing/power = broken parts.

  8. #8
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    Pardon me, I was just pickin' my jaw up off the floor!

    You da man, Snook!
    Am I done yet? The wife keeps telling me yes!

  9. #9
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    wow dude your a talented
    Last edited by Double G; 06-11-2014 at 07:33 AM. Reason: language
    you must be fast, you were right behind me

  10. #10
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    Great job Snook Man. Very talented and way to think out of the box (Transmission).
    FLM Tmaxx 3.3, Nitro Sport 2.5R, Electric Rustler.

  11. #11
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    Wow. That's a lot harder than I thought it would be (both coming up with it and actually doing it). I don't have the tools or the skills to do this . If you start making them to sell, and if the price isn't an arm and a leg (for the amount of work I think it warrants at least a leg ) I would buy one.
    Oh where'd you go, Joe DiMaggio?

  12. #12
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    +1 I would by one right now! Super cool, and a great job Snook Man...........

  13. #13
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    Cool cool cool....really cool man. nicely done. Come on make some for us as well.

  14. #14
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    How well can the modified primary gear last against the steel 3rd gear?

  15. #15
    RC Turnbuckle Jr. Snook Man's Avatar
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    I have had no problems yet. Lots of people run the RRP steel gears mixed with the stock plastic and don't have problems.

    It's a work in progress and have more testing to do but I'm getting closer to the light at the end of the tunnel
    No slipper/tall gearing/power = broken parts.

  16. #16
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    That is incredible and, I believe, the first of its kind? I would love to know how the case holds up now that its been cut with the forstner bit. I was thinking... since the main cut in step one involves being centered over the bearing, how about using a good quality hole saw with a pilot bit that fits the bearing? This would center that first cut nicely.

    Excellent job! I have a spare tranny that I gotta try this on. A great addition to my already insane S-Maxx!!!
    Phs 2 S-Maxx build- 24/54 gears. Can U say faster?

  17. #17
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    All i have to say it WOW.......
    T-Maxx 3.3 = 4yr old
    HPI RS4 = 3yr old

  18. #18
    RC Turnbuckle Jr. Snook Man's Avatar
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    Quote Originally Posted by T-MAXXTER
    since the main cut in step one involves being centered over the bearing, how about using a good quality hole saw with a pilot bit that fits the bearing? This would center that first cut nicely.

    Excellent job! I have a spare tranny that I gotta try this on. A great addition to my already insane S-Maxx!!!
    The tranny case is doing well, I cant tell a differance in strengh with the removal of the plastic.

    If you use a hole saw make sure it is well ballanced with no wobble or it will grab the plastic and make it difficult to get a clean cut.
    Take the time to make a jig to hold the housing level and square with the drill press bench and one that you can clamp to the bench. It took me about an hour to make my jig setup and only 20 seconds to do the cut.

    It will make a great addition the that SMaxx of yours...Hang on when she hits
    3rd
    No slipper/tall gearing/power = broken parts.

  19. #19
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    Wow, nice work!

    Think this will hold up to brushless power?
    For some reason, my old .18 t'e-maxx conversion won't go into second and I'm considering extending the chassis and going 3-speed.

  20. #20
    RC Turnbuckle Jr. Snook Man's Avatar
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    Probably will not hold up to brushless unless you use all steel gears.
    The stock 1st and 2nd gear sets are just too narrow to hold up to BL torque.
    If you were only doing speed runs and set the punch control up to not hammer the gears too hard it should hold up for a while.
    No slipper/tall gearing/power = broken parts.

  21. #21
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    PHENOMENAL!!AWESOME DISPLAY OF YOUR KNOWLEDGE AND CREATIVITY !!
    I have to say that your brain works in a way that not many others can comprehend. I am absolutely beside myself with your illustration and direction.
    Thank you for making me feel dumber today.
    How does it go? ...Creativity is the mother of all invention.
    Im not kissin butt , just in awe at what can be done with some thought.
    Very good job........Watch out TRAXXAS may put a hit out for you.
    Or offer you a lucrative position in the R & D dept.
    Keep the shiny side up!

  22. #22
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    Snook
    how much would you charge to supply a 3speed trany?
    You are off the hook with knowledge, un frign smart!

  23. #23
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    Quote Originally Posted by chrispycracker
    Snook
    how much would you charge to supply a 3speed trany?
    You are off the hook with knowledge, un frign smart!
    You should consider making these to sell. Or at least selling your design to a company so that they can make them to sell. I think that you should design a tranny case so that you wouldn't have to keep modifying stock tranny cases. I know I have already said something to this effect, but you really did an amazing job with this! Totally awesome. I too am in awe of your skill and creativity. Good job!
    Oh where'd you go, Joe DiMaggio?

  24. #24
    RC Turnbuckle Jr. Snook Man's Avatar
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    First batch of parts are due to arrive the 2nd week of May.
    It's slowly becoming a reality.
    No slipper/tall gearing/power = broken parts.

  25. #25
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    Quote Originally Posted by Snook Man
    First batch of parts are due to arrive the 2nd week of May.
    It's slowly becoming a reality.
    Awesome !
    Oh where'd you go, Joe DiMaggio?

  26. #26
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    tmaxx 2.5 tranny 3 speed conversion

    Hi,saw your 2.5 tranny 3 speed conversion.Simply,BRILLIANT.
    Wonder if you would be kind enough to make one for me.How much would it cost to buid one and to ship to Singapore.
    Greatly appreciate your help and expertise.

    Thanks.
    P.S. My email:c_segeran@yahoo.com.sg

  27. #27
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    Stallion, this is something for a PM (Personal Message) not a post in an old thread. But that's OK, just letting you know. Welcome to the forum!

    And yes, Snook Man is brilliant. This is some piece of work, but I've come to expect great things from him, so I'm highly impressed but not surprised. Its a mechanical masterpiece of MAXX modification!
    Oh where'd you go, Joe DiMaggio?

  28. #28
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    Great right up! After I get my maxx awake I think im going to try it. I have a 2.5 and a .15

    Would this better benefit an engine with more torque or more rpm? I have a .15 im building (bought as a roller) and a 2.5 (as a poor runner) that im going 2.5r or 3.3 and need to know what one?
    People Eating Tasty Animals

  29. #29
    RC Turnbuckle Jr. Snook Man's Avatar
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    You will want to gear down with the CB/SG using either the 2.5R or 3.3. The 3.3 has just enough for the shift change with 20T/72T cb/sg and then will struggle under the load.

    18T/72T works better and allows the engine to spool up easier once you hit 3rd.
    More torque is always better imo.

    I wouldn't consider a .15 engine and a 3 speed, it would fall on its face after the shift change into 3rd.
    No slipper/tall gearing/power = broken parts.

  30. #30
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    Sounds good thanks.
    People Eating Tasty Animals

  31. #31
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    Ever thought about doing it with a revo trans? Awesome build though. I wonder how it would handle with a O.S. .21. Or maybe even a big block since you'll need a lot of rpm's. Have you done speed runs with the trans? What'd you reach with what gearing? Kinda makes me want to get a tmaxx just to do this.
    Revo 2.5 upgraded to 3.3.

  32. #32
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    Quote Originally Posted by ManDime View Post
    Have you done speed runs with the trans? What'd you reach with what gearing? Kinda makes me want to get a tmaxx just to do this.
    He had another build that I believe the transmission went into: http://traxxas.com/forums/showthread...MPH-Challenge/
    The Super Derecho

  33. #33
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    Quote Originally Posted by Double G View Post
    He had another build that I believe the transmission went into: http://traxxas.com/forums/showthread...MPH-Challenge/

    well the speed run was down with the 2 speed rather than the 3speed but for 108 mph, that's not bad.... It took me 40 minutes to read that thread.....
    Revo 2.5 upgraded to 3.3.

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