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Thread: Mod-1 Tranny

  1. #1
    RC Qualifier Synnergy's Avatar
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    Mod-1 Tranny

    Greetings all,

    Let's try and figure out this tranny mod. This sounds like a fun challenge. The goal is to have a stronger tranny with Mod-1 gears. I think the top drive, idler, and diff could all be mod-1...but I am wondering about the diff internal gears (the planetary and sun gears.) I have seen two mod-1 trans videos and both of them got rid of the diff...I would rather see a diff in there. What do you think?

    Here's what I am thinking:

    Top Drive Shaft/Gear: Maybe have a gear manufactured...or maybe find a gear that would work already.

    Idler Gear: I am going to look at having an idler made that would allow for the two bearings to fit into.

    Diff: I am thinking about having a mod-1 "cog" gear made that would replace a HR cog gear.

    Diff Internal gears: What do we do here? Do we have some hardened steel gears made? For those of you who have had the diff gears strip, is it the planetary gears or the sun gears that strip? Or both.

    Let's do this!
    MTFBWY

  2. #2
    RC Qualifier Synnergy's Avatar
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    Traxxas part #3793, this is the top drive shaft. What is the diameter of that shaft? 5mm?
    MTFBWY

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    RC Qualifier MAC FAB's Avatar
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    Yup, 5mm. 5x11x4 bearings. Those will be the next weak link. Doing indoor carpet wheelies grenaded one in my car. See the exploded view in the model selection. I just printed the exploded view so I have a copy for reference.

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    There was a guy on YouTube with a mod1 trans, but he would not say how he did it. I also saw some on the Facebook group RC Junkies. All that I have seen use a spool, but it would be awesome to get an open diff with stronger internal gears and mod1 outer gear. Would be a Christmas miracle if TRX came out with a SL2SH 2.0 that uses 32p transmission gears and a redesign diff to be stronger.

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    https://m.youtube.com/watch?v=wfvxiJbz0vE
    https://m.youtube.com/watch?v=XInPZI0wRj4

    Here are a couple videos of the mythical mod1 gearbox

    Maybe we can reverse engineer these videos.

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    https://m.youtube.com/watch?v=41OuVRrksA0

    A better view of the beast

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    The issue has always been and always be the diff. None of these guys have really done anything special. I have the FLM,HR, and the HR spool. To eliminate the diff is silly in almost every application. Iím running currently an FLM diff case with 100k wt oil. That paired with know the limits and driving to suit them, I love it. Iíve blown the diff gears in my HR case three times. When it blows, the case is trash. Steel beats aluminum every time.
    Love how these tool bags say they wonít show you how they did things. You put gears in a tranny that didnít break to begin with and eliminated the diff. Way to go, now try to turn(not donuts). Sorry for the rant, but Iím over it.

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    RC Qualifier Synnergy's Avatar
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    Quote Originally Posted by MAC FAB View Post
    Yup, 5mm. 5x11x4 bearings. Those will be the next weak link. Doing indoor carpet wheelies grenaded one in my car. See the exploded view in the model selection. I just printed the exploded view so I have a copy for reference.
    Are you saying that the bearings need improving? Are there stronger bearings? If there are some stronger 5x11x4 bearings I'd be down with that. I don't want to change the size of the bearings that fit in the trans case...it would get too complicated and expensive...we need to work with what we have there. What do you think? Stronger bearings?
    MTFBWY

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    Quote Originally Posted by SL4SHGT8BASHER View Post
    I'll be checking those vids out, thanks!
    MTFBWY

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    RC Qualifier Synnergy's Avatar
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    Quote Originally Posted by Gripdog7205 View Post
    The issue has always been and always be the diff. None of these guys have really done anything special. I have the FLM,HR, and the HR spool. To eliminate the diff is silly in almost every application. I’m running currently an FLM diff case with 100k wt oil. That paired with know the limits and driving to suit them, I love it. I’ve blown the diff gears in my HR case three times. When it blows, the case is trash. Steel beats aluminum every time.
    Love how these tool bags say they won’t show you how they did things. You put gears in a tranny that didn’t break to begin with and eliminated the diff. Way to go, now try to turn(not donuts). Sorry for the rant, but I’m over it.
    I was thinking we could have the center piece of the HR diff manufactured mod-1 (I ink they call this the cog,) I'm not sure what do with the solar and planetary gears. Which ones break more often the solar or planetary?

    I know how you feel about them not sharing...let's do this and share it!

    I have a few things on order, a few hr diff cases as well as a few mod-1 gears. I also ordered some of the stock internals for comparrison purposes.

    The top drive is the first I'm considering. I'm wondering if there is a modifiable pinion gear that we could use. If we could modify an existing gear it might be cheaper than having some made. In one of the videos they used an 11 tooth gear for the top drive. I have a few on order to check the dimensions.

    Tomorrow I'll do some measuring, and maybe go visit a manufacturing place here in Milwaukie OR. On their website there is a picture of a stock diff that looks like a traxxas 2wd! Maybe someone already had the sun and planetary gears made and perhaps they still have the design. We'll see.
    Last edited by Synnergy; 04-20-2018 at 01:14 AM.
    MTFBWY

  11. #11
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    Quote Originally Posted by Synnergy View Post
    I was thinking we could have the center piece of the HR diff manufactured mod-1 (I ink they call this the cog,) I'm not sure what do with the solar and planetary gears. Which ones break more often the solar or planetary?

    I know how you feel about them not sharing...let's do this and share it!

    I have a few things on order, a few hr diff cases as well as a few mod-1 gears. I also ordered some of the stock internals for comparrison purposes.

    The top drive is the first I'm considering. I'm wondering if there is a modifiable pinion gear that we could use. If we could modify an existing gear it might be cheaper than having some made. In one of the videos they used an 11 tooth gear for the top drive. I have a few on order to check the dimensions.

    Tomorrow I'll do some measuring, and maybe go visit a manufacturing place here in Milwaukie OR. On their website there is a picture of a stock diff that looks like a traxxas 2wd! Maybe someone already had the sun and planetary gears made and perhaps they still have the design. We'll see.
    Planet gears are pretty easy to shred. That being said, I havenít blown a diff in a while now, knock on wood.

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    RC Qualifier MAC FAB's Avatar
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    Quote Originally Posted by Synnergy View Post
    Are you saying that the bearings need improving? Are there stronger bearings? If there are some stronger 5x11x4 bearings I'd be down with that. I don't want to change the size of the bearings that fit in the trans case...it would get too complicated and expensive...we need to work with what we have there. What do you think? Stronger bearings?
    My application beats up the output bearings. One of my inners grenaded when I was driving inside on carpet and decided to do wheelie runs. Quite funny until it quit moving. Run all this in an aluminum case and all is probably well. Again, I am driving a 10 lb car so the problems I have may be specific to the car's weight, no clutch and pinned throttle. Needle bearings would be way better, but your tranny will end up costing $500 or more because of the work involved and because they could charge that. Bulletproof, but buyers? Doubt there would be many peeps willng to drop that for a 2wd tranny when most people already cram big horsepower into the 4wd format. The key to making this happen is to keep it inexpensive.

  13. #13
    RC Qualifier Synnergy's Avatar
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    I just spoke with the owner of a local gear manufacturing shop. I need to go visit in the next few days. Just a note that I haven't forgot. A few of my parts came in, so I have examples of what we need.

    I'll post an update after I visit the shop.
    MTFBWY

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    Anyone know how the solar gears are made? I tried to knock the gear off the shaft...but it seems like it is one piece.
    MTFBWY

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    update: I finally made it to the gear manufacturing shop. Looking at the "cog" gear of a hot racing diff it looks like there isn't room to do a mod-1 gear there. This may be the area to focus on as the limiting factor. There may be room to do 32 pitch. Obviously if the diff is 32 then the idler and top drive also need to be 32. The diff internals (planetary and solar,) might be able to have 32 pitch...or the internals may just need to be heat treated, but the diff internal gears are not big enough to do a mod-1. Heat treated hardened 32 pitch gearing may be a good compromise.

    It would cost about $150 to heat treat a pile of gears...fyi.

    The next step is to leave a complete transmission and see what they think.
    MTFBWY

  16. #16
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    Quote Originally Posted by Synnergy View Post
    update: I finally made it to the gear manufacturing shop. Looking at the "cog" gear of a hot racing diff it looks like there isn't room to do a mod-1 gear there. This may be the area to focus on as the limiting factor. There may be room to do 32 pitch. Obviously if the diff is 32 then the idler and top drive also need to be 32. The diff internals (planetary and solar,) might be able to have 32 pitch...or the internals may just need to be heat treated, but the diff internal gears are not big enough to do a mod-1. Heat treated hardened 32 pitch gearing may be a good compromise.

    It would cost about $150 to heat treat a pile of gears...fyi.

    The next step is to leave a complete transmission and see what they think.
    You think heat treating hardened steel is a worth while endeavor? Iím really asking honesty. Iíd be willing to throw some money if the shop feels like they can make a stronger gear. I can shred mine at will now.

  17. #17
    RC Qualifier Synnergy's Avatar
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    I think heat treatment is the minimum we should consider and I'm hoping we can get some 32 pitch gears made. I figured you'd be willing to test out whatever we get.

    The rr steel idler is a hardened steel...and it seems a lot better than the stock steel idler (the stock IS steel correct?). So I figure heat treating is worth it to some extent.

    Those small teeth on the planetary gears are so tiny! They need to be bigger...do you think 32 pitch would be significantly stronger? Maybe 32 AND heat treated.

    When you shred your gears which ones are damaged?
    MTFBWY

  18. #18
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    Quote Originally Posted by Synnergy View Post
    I think heat treatment is the minimum we should consider and I'm hoping we can get some 32 pitch gears made. I figured you'd be willing to test out whatever we get.

    The rr steel idler is a hardened steel...and it seems a lot better than the stock steel idler (the stock IS steel correct?). So I figure heat treating is worth it to some extent.

    Those small teeth on the planetary gears are so tiny! They need to be bigger...do you think 32 pitch would be significantly stronger? Maybe 32 AND heat treated.

    When you shred your gears which ones are damaged?
    I think 32 would be better. I donít think they can be cut deeper. A proper heat treatment would surely help. The stock is steel. I swapped to the RR long before swapping to 1:8 electronics. Iíve never had an issue with any other gears than the diff gears.
    I shred the planets and the suns

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    Ive shredded those gears on just a castle sct with 3800kv lol. Just takes tightening the slipper down all the way and a few wheelies.

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    Quote Originally Posted by User View Post
    Ive shredded those gears on just a castle sct with 3800kv lol. Just takes tightening the slipper down all the way and a few wheelies.
    Any insight into the thread though?

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    RC Qualifier MAC FAB's Avatar
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    I suppose heat treating is cheaper on mild steel than some 300m gears, right? Talk to the gear guy. Then you have to ask yourself, "Do I want to have $500 tied up in a Slash tranny when its all said and done, and still only has 5mm out flanges?

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    RC Qualifier Synnergy's Avatar
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    Quote Originally Posted by MAC FAB View Post
    I suppose heat treating is cheaper on mild steel than some 300m gears, right? Talk to the gear guy. Then you have to ask yourself, "Do I want to have $500 tied up in a Slash tranny when its all said and done, and still only has 5mm out flanges?
    What are 300m gears? To get all the gears made it will probably be more than 500, although after all the setup is done it will be much cheaper. The solar gears/output shafts/outdrives will need to be made, what size shaft should we consider? Do you have any suggestions on the size and then what axles would you suggest?
    MTFBWY

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    RC Qualifier MAC FAB's Avatar
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    300m is a material. Class 1 buggy axles, micro stubs, hub components and the like. The more bullet proof stuff. If they can machine them from it, that would be the end of the story. Cost would probably kill that from ever happening. 4130 would work for us as well. Would anything in a Slayer tranny cross over for the better?

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    I'll check on the 300m material and other strong/hard materials they might be able to use. I think I'll focus on the diff for now. I know people have destroyed idlers as well as the top drive, but the diff internal gears are the weakest link at this point.

    If we have the option of making a custom solar/output shaft, should we stick with the 5mm flange or is there a better option? It would be nice to keep it close to stock size...but I'd like to hear other ideas. IF we changed the flange, what axles would be available?
    MTFBWY

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    Quote Originally Posted by Synnergy View Post
    I'll check on the 300m material and other strong/hard materials they might be able to use. I think I'll focus on the diff for now. I know people have destroyed idlers as well as the top drive, but the diff internal gears are the weakest link at this point.

    If we have the option of making a custom solar/output shaft, should we stick with the 5mm flange or is there a better option? It would be nice to keep it close to stock size...but I'd like to hear other ideas. IF we changed the flange, what axles would be available?
    The tranny case would have to be modified to accommodate larger bearings if diameters are increased. I donít like a bearing thatís too thin.

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    RC Qualifier MAC FAB's Avatar
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    6mm lets you run E Revo or E Maxx axles. $25 +/- for the set. Would handle all the power you could fit into the tranny case. Just need to make the outputs just a tad longer than the stock Slash. The bigger question then is does Avid have the bearings to pop into the aluminum tranny case to allow this to happen. I believe HR makes the uprights that allow for a 6mm axle. Someone does, they did it on the rear of a 4x Slash. No rotating mass for the Revo axles, nothing to get out of balance. You just need to trim to length. Same for the E Maxx, they are just a little less beefy but wicked strong and no mass again. Kiss MIP axles god bye. Heck, you could run Summit cvds, trim to fit and again no rotating mass. A speedsters dream. This brings me full circle on the thought process. For what vehicle "purpose" (more of a why) would you be putting this tranny into your truck? Would it be easier and cheaper to shoehorn an E Maxx diff with a custom motor/trans mount than building this Slash deal. Accomplishes all the above. Mesh pinion gears on the trans input and motor shaft. Hmmmm........

  27. #27
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    Quote Originally Posted by MAC FAB View Post
    6mm lets you run E Revo or E Maxx axles. $25 +/- for the set. Would handle all the power you could fit into the tranny case. Just need to make the outputs just a tad longer than the stock Slash. The bigger question then is does Avid have the bearings to pop into the aluminum tranny case to allow this to happen. I believe HR makes the uprights that allow for a 6mm axle. Someone does, they did it on the rear of a 4x Slash. No rotating mass for the Revo axles, nothing to get out of balance. You just need to trim to length. Same for the E Maxx, they are just a little less beefy but wicked strong and no mass again. Kiss MIP axles god bye. Heck, you could run Summit cvds, trim to fit and again no rotating mass. A speedsters dream. This brings me full circle on the thought process. For what vehicle "purpose" (more of a why) would you be putting this tranny into your truck? Would it be easier and cheaper to shoehorn an E Maxx diff with a custom motor/trans mount than building this Slash deal. Accomplishes all the above. Mesh pinion gears on the trans input and motor shaft. Hmmmm........

    Not clean, but this is why. Itís a work of art. Not a piecemeal rat rod. This is my reasoning.

  28. #28
    RC Qualifier MAC FAB's Avatar
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    What happened to that? I'm not referring to piece meal rat rodding. In fact, IMHO rat rods are not my cup of tea.. Mounting a motor onto the E Max isn't rat rod, looks more like your modern class 1 car with a big LS motor mounted to an Albins, Fortin or Mendiola mega $$$$$ transaxle. Maybe it isn't the ideal street format, but the r&p in the E Maxx diff is beefy. My suggestion is to simply have something that will handle the power you want to put through it and not cost a fortune. My builds weigh between 8 and 10 lbs, pushing 2s batteries to their limits. Jumped to 3s and now you'd think I was running my 410ci LS thru a stock bug trans. Snap, crackle, pop. UDR races in the desert format will be just a matter of time. The hybrid "rat rod" deal a buddy and I came up with works flawlessly, you just have to run it mid motor which probably won't work in a standard Slash.

  29. #29
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    Quote Originally Posted by MAC FAB View Post
    What happened to that? I'm not referring to piece meal rat rodding. In fact, IMHO rat rods are not my cup of tea.. Mounting a motor onto the E Max isn't rat rod, looks more like your modern class 1 car with a big LS motor mounted to an Albins, Fortin or Mendiola mega $$$$$ transaxle. Maybe it isn't the ideal street format, but the r&p in the E Maxx diff is beefy. My suggestion is to simply have something that will handle the power you want to put through it and not cost a fortune. My builds weigh between 8 and 10 lbs, pushing 2s batteries to their limits. Jumped to 3s and now you'd think I was running my 410ci LS thru a stock bug trans. Snap, crackle, pop. UDR races in the desert format will be just a matter of time. The hybrid "rat rod" deal a buddy and I came up with works flawlessly, you just have to run it mid motor which probably won't work in a standard Slash.
    6S happened. Thatís number 4 I think. Iíd love to find some gears(thatíll last) to fit my current setup. Really the Rustler that thatís in really only sees pretty straight roads. I have no issues unless theyíre self inflicted. 10 bucks and 40 minutes and Iím back up and running.
    I do see your point.

  30. #30
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    This is an interesting thread, it's got me thinking.
    I'm going to harden the stock planetaries next time I blow a diff, it doesn't happen to me enough for a mod the caliber being discussed since the hardest I run is 4s with 23/56 gears but harder gears will definitely be a positive move forward.

    Thank you for the idea gentlemen.
    Built Ford Tuff With Chevy Stuff.

  31. #31
    RC Qualifier MAC FAB's Avatar
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    The only potential problem with hardening the gears would be the material they are made of. If my brain is working correctly, they may not harden (heat treat anyhow), or could become brittle which would be worse than stock.

    Gripdog, did your motor come off and the pinion gear do the dremel port and polish on that case? I like the clearance job so you can run the tiny spurr, I did that as well.

  32. #32
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    Quote Originally Posted by MAC FAB View Post
    The only potential problem with hardening the gears would be the material they are made of. If my brain is working correctly, they may not harden (heat treat anyhow), or could become brittle which would be worse than stock.

    Gripdog, did your motor come off and the pinion gear do the dremel port and polish on that case? I like the clearance job so you can run the tiny spurr, I did that as well.
    Nah. I had it torn down. FLM used nice aluminum, it made the job easier to do well. Good eye btw. Iím running 34/34

  33. #33
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    The only potential problem with hardening the gears would be the material they are made of. If my brain is working correctly, they may not harden (heat treat anyhow), or could become brittle which would be worse than stock.
    Yes there is a definite risk of this happening but I figure theres not but $7 bucks to lose if it fails but a lot to gain if successful.
    Built Ford Tuff With Chevy Stuff.

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    Quote Originally Posted by Gripdog7205 View Post
    Any insight into the thread though?
    Could just torch the gears and dip them in oil. Other than that I’m not sure there is a reasonable/ affordable way to accomplish the without just findin a way to fit an already existing mod-1 tranny to the chassis.

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    Quote Originally Posted by billy-bones View Post
    Yes there is a definite risk of this happening but I figure theres not but $7 bucks to lose if it fails but a lot to gain if successful.
    I’m pretty sure sintered metal just gets brittle with heat treatments.

  36. #36
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    Quote Originally Posted by User View Post
    I’m pretty sure sintered metal just gets brittle with heat treatments.
    Thanks, I've been doing some research and not going to bother with it.
    I can get a season out of two three sets of gears so it won't break the bank to have a couple sets on hand.
    If I decided I needed them to last a bit longer simply treating the truck kinder would work too.
    Built Ford Tuff With Chevy Stuff.

  37. #37
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    Quote Originally Posted by billy-bones View Post
    Thanks, I've been doing some research and not going to bother with it.
    I can get a season out of two three sets of gears so it won't break the bank to have a couple sets on hand.
    If I decided I needed them to last a bit longer simply treating the truck kinder would work too.
    Well thatís no fun.

  38. #38
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    Quote Originally Posted by Gripdog7205 View Post
    Well that’s no fun.
    LOL! Thats why I always keep a set or two on hand.
    Built Ford Tuff With Chevy Stuff.

  39. #39
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    Quote Originally Posted by billy-bones View Post
    LOL! Thats why I always keep a set or two on hand.
    Me too. Just used my last one. Need to reorder

  40. #40
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    Quote Originally Posted by billy-bones View Post
    LOL! Thats why I always keep a set or two on hand.
    I'm currently out of sets....... complete transmissions that is, which have been robbed for parts. I have a diff I need to take apart and get pictures of the carnage, should be interesting. And all I want is to go 30 mph...... and not break. Spool is looking way more attractive.

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