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Thread: Diff-seal mod

  1. #1
    RC Qualifier Synnergy's Avatar
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    Diff-seal mod

    Greetings All!

    I have seen some methods for modifying the stock Traxxas differential to "seal" it and I wanted to take a stab at it. I watched a few how-to videos which gave me a couple of ideas. I have several HR diffs working in some RCs, and this has left me with several old and new stock diffs. I started thinking to myself, "what are you going to do with all these stock diffs?"

    I know there's more traffic on the other parts of this forum, and I want to reward the brave stampede owners who frequent this area. I'm not 100% sure this will work as I have not tested it yet...but my first completed diff seems pretty good.

    Here's the completed diff as well as the tools I used:



    I did leave a bit of extra around the 2 "slot/groove" parts of the housing. The first step is to bevel the output holes on each side. This will allow the larger drill bit to fit evenly. Oh yeah, and I did all the drilling by hand, it didn't take much force (as the bits are sharp,) and it allows you to take your time.




    That's a 3/8" counter-sunk drill bit. The next step was to use a drill bit to give the area the right contour to accept the o-ring.




    Again, I drilled it by hand nice and easy. It didn't take long, and I would think using a power drill would be a bit reckless. That's a 5/16" bit. I kept trying in the o-ring until I was happy with how much was sticking out, I lowered it a bit further than the picture here:



    I placed a "shim" (washer) in between the outputs, I do this on the HR diffs as well. It reduces the horizontal play significantly. The last HR diff I built I didn't use the HR shims that came with it...I ended up using a washer about this size in the pic. There was too much play without it, and I wonder if this is why some folks are having their HR diffs leak.



    For those of you who have used the HR diffs, you know that the output shafts have an o-ring on them. I found two sizes to be about right and I like the 4mm x 8mm o-ring. ACE hardware had a standard sized o-ring, but I liked the metric one better, it was a little fatter. I placed some of the 100k diff oil on the o-ring before assembly. I did clean the gears before assembly. Also, around the plastic rim of the housing I swiped some sealer before placing the housing together.

    If it works, it will save $50-70 for a sealed alloy diff. It should also be slightly lighter than the metal ones.

    Adios for now, and May the Force be With You.

  2. #2
    RC Champion lektro's Avatar
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    Nice work. So I have a question after seeing the o ring you installed. I take it this did not cause any binding of the gears/shafts, when you re-assembled? Did you use a PTFE shim/washer between the gear and the oring? It would probably be a bit more slick than metal to rubber and reduce wear on the o ring.
    Last edited by lektro; 03-08-2018 at 07:28 AM.
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  3. #3
    RC Qualifier Synnergy's Avatar
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    Quote Originally Posted by lektro View Post
    Nice work. So I have a question after seeing the o ring you installed. I take it this did not cause any binding of the gears/shafts, when you re-assembled? Did you use a PTFE shim/washer between the gear and the oring? It would probably be a bit more slick than metal to rubber and reduce wear on the o ring.
    Whatup Lektro! No, there wasn't any binding of the gears...everything was moving well. This mod mimics the HR diff, and other than the case being plastic versus the al of the hr case there isn't a difference with how the O-rings fit on the sun gears. I may have used too big of a shim on the sun gear shaft...it may not have needed that at all...

    I didn't have a completed HR diff that was out of a case to compare with...but the action of the diff outputs seemed very similar to the other ones I have put together.

    I have heard that the heat sink quality of the aluminum diff is significant but I don't think I put that amount of heat through my vehicles.

  4. #4
    RC Qualifier Synnergy's Avatar
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    I see I didn't answer your question about the washer over the o-ring. No, I didn't use a washer over the o-ring. Neither does the HR diff. I did see in other mod styles that people used that when it was on the outside of the diff case...but I don't think it is necessary...maybe it would be a good idea...I would probably make the o-ring sit a little deeper if I were to use the 1985.

  5. #5
    RC Qualifier Sp2deSummit's Avatar
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    I just did this to my rustler diff and filled it with 60000w oil, will see how it does. How has this mod worked out for you Synnergy? Thanks for the tips by the way
    I like free stuff!

  6. #6
    RC Qualifier Synnergy's Avatar
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    Whatup Sp2deSummit!
    Only one of the stock-sealed diffs leaked (I think I did about 6 of them,) but I think it is because I overfilled it! I like the HR diffs, and I haven't had any leaks yet, but the stock diffs are lighter and if you have them laying around I think this is a good use for them. The lightest oil I have tried is 30K, most of them have 100K.
    MTFBWY

  7. #7
    RC Qualifier Sp2deSummit's Avatar
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    Sweet, it works! I only have that 60k, but it's all I need. Tested it out today, MUCH less diff action, which is exactly what I wanted. Plus, only cost me $9, and some extra time
    I like free stuff!

  8. #8
    RC Champion zedorda's Avatar
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    I wonder if using a dremel and a stone ball grinding bit would make a better o-ring seat than a drill bit? And if I can cut a latex glove to make a gasket.
    Last edited by zedorda; 10-15-2019 at 08:24 PM.

  9. #9
    RC Qualifier Sp2deSummit's Avatar
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    Quote Originally Posted by zedorda View Post
    I wonder if using a dremel and a stone ball grinding bit would make a better o-ring seat than a drill bit?
    Probably, but sounds more time consuming. For me, if it still seals, I'll keep on drilling until it doesn't work.

    Quote Originally Posted by zedorda View Post
    And if I can cut a latex glove to make a gasket.
    Heh heh, whatever works for you If I tried that, cutting the little circle would be more of a box shape...
    I like free stuff!

  10. #10
    RC Qualifier Synnergy's Avatar
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    Quote Originally Posted by zedorda View Post
    I wonder if using a dremel and a stone ball grinding bit would make a better o-ring seat than a drill bit? And if I can cut a latex glove to make a gasket.
    Try it if you have the tools available, sounds good!
    MTFBWY

  11. #11
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    Depending on the grinding bit, it may be too rough and/or melt it. I like the by hand approach.
    Either that or a steel bit on a drill press where you could care fully control and duplicate the depth.
    Looks like Synnergy got it pretty smooth, but my guess not perfectly smooth or true.
    But the O rings take up the defects most of the time by the looks of the results.
    Ideally you would get the right ball mill to match the curve radias and Diameter size of the O ring.
    I like this mod! Latex glove gasket??? Sounds interesting. I'll be looking for the test results...

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