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  1. #1
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    Pitch of differential pinion

    I have p/n 4981, and needed to know the differential pinion pitch or modulus. I'm trying to use the differential pinion but instead of connecting it to the ring gear, I need to connect it to a similar bevel gear like this - https://www.amazon.com/0-250-inch-Bo...s%2C134&sr=8-2. I'm trying to build a very specific type of pulling truck with most of the driveline from the T-Maxx. What type of bevel gear could I get that would mate with the differential pinion 4981?
    Last edited by sfortner; 10-30-2019 at 11:42 AM.

  2. #2
    RC Qualifier Flux Capacitor's Avatar
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    Does the bevel gear have to have a hole or a shaft? The reason I ask, is because differential pinions will mate to differential pinions in a hypoid type setup but have to be possibly cut and drilled (fabricated to mate) since they contain a shaft.
    Last edited by Flux Capacitor; 10-30-2019 at 12:02 PM. Reason: Correction.
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  3. #3
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    In this case, I have a 1/4" axle I'm wanting to attach to a bevel gear with a set screw or clamp. I had originally planned to use the differential/ring gear, but it's too big around. I really need something like the bevel gear link I attached so it can fit in my pan car axle/hub design. I'd prefer something like the traxxas differential pinion gear but instead of being on a shaft, it would need to have a bore so it can be attached to my 1/4" axle.

  4. #4
    RC Qualifier Flux Capacitor's Avatar
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    Quote Originally Posted by sfortner View Post
    In this case, I have a 1/4" axle I'm wanting to attach to a bevel gear with a set screw or clamp. I had originally planned to use the differential/ring gear, but it's too big around. I really need something like the bevel gear link I attached so it can fit in my pan car axle/hub design. I'd prefer something like the traxxas differential pinion gear but instead of being on a shaft, it would need to have a bore so it can be attached to my 1/4" axle.

    That is slick if you could find what you need. I understand better what you are trying to do now and the only thing I can think of is major fabrication work in your future as that is very custom and rare to come across a bevel gear that is going to compensate both the pitch of a pinion and space limitations.

    Also, I'm sorry that I didn't let you know that I don't know the pitch or modulation of the pinion which was one of your original questions. Someone on here may know.
    Last edited by Flux Capacitor; 10-30-2019 at 04:01 PM.
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  5. #5
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    Yeah, agreed. I'm having a really hard time getting all this to match up. I made the mistake of trying to match up parts from different vendors from different trucks and it was a disaster. The gear pitches are very different especially when you pick different scale trucks. Some 1/16 scale trucks have lower pitch diff gears like the Redcat vs the 1/16 E-Revo, which is a very fine pitch. If I could stay with all Traxxas parts, that would be sweet, because I totally have the driveline mapped out where I have a worm gear drive on a brushless outrunner with a center transmission for a very slow axle speed, and the related worm wheel bolted to a 4981X spool in the center then on each end. I'm using T-Maxx diff yokes off each of the spool, to the sliding drive shafts then to another diff yoke on the other end, which I can connect to the differential pinion gear p/n 4981. From there, I run out of parts. There's no way I know of getting something like a 13 tooth differential pinion on the 1/4" drive shaft.

    I could maybe do the fabrication you're talking about with matching bevel gears like these? https://www.amazon.com/CNBTR-Steel-S...K25C1KMF5YK12F

  6. #6
    RC Qualifier Flux Capacitor's Avatar
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    Quote Originally Posted by sfortner View Post
    I could maybe do the fabrication you're talking about with matching bevel gears like these? https://www.amazon.com/CNBTR-Steel-S...K25C1KMF5YK12F

    That is along the lines of what I was thinking - yes.

    Fabricate something up that matches bevel to bevel in order to eliminate pitch worries. That was the only idea I had because if you can't find something to work like that, you are looking at serious machining fabrication of parts; not just matching up bits and pieces to finish the end result.
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  7. #7
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    Thanks for all the feedback. Iíll see what I can find because Iíd love to just use the Traxxas center driveline and take that to a bevel gear if I can find the pitch. May yíall to some machine shop or gear guys and maybe I can determine the pitch/modulus of the Traxxas differential pinion and buy what is needed to match up with it. Iíll keep you posted. Iím sure thereís a way to determine that pitch.

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  9. #9
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    Thanks Double G - that's actually very helpful. I hope this works for bevel gears, but it looks like it may have. The Traxxas T-Maxx differential pinion has 13 teeth and measured 0.575 inches on the outside with my calipers, which translated to 14.605 mm. The site calculates it at a metric module of 0.97 and a diametral pitch of 26.2. That sounds feasible - that probably rounds to a modulus of 1.0, and I can definitely get gears with that configuration.

    When I run this gear with the 15 teeth and 16mm outer diameter through the site, it calculates a 0.94 module and 27 pitch so that's probably a match!

    These gears look to be a smaller 20 tooth, and there's two of them, but at a 6mm bore, but still a 1.0 modulus - https://www.amazon.com/dp/B06Y5MYTTZ...dDbGljaz10cnVl.

    Here's another idea that would work too but I don't like the idea of a timing belt pulley drive, but there's some R/C vehicles that are using this with success today, One review talked about how strong it was and I'm sure it would handle quite a bit of torque. My truck is 1/24 scale so it would probably work fine. But I've got a 1 HP brushless outrunner on it though...
    Last edited by sfortner; 10-31-2019 at 09:12 PM.

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