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  1. #1
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    Ultimate Summit Differential Upgrade

    Hello all! I am new to these forums, but here's what's up:

    I have what I hope is good news for all of you. One of my good friends, who I believe is a member on these forums (though he said he hasn't been on for a while) has got quite the project brewing. He is a CNC machinist by trade here in Colorado. I was able to head down to the shop this morning to talk with him and after a bit the conversation turned to the interesting things he's working on. I am a Summit owner myself, as is he, so naturally we talked about the potential there. It turns out he's already put a lot of thought into differential/driveline upgrades for this truck. I don't know too many details right now. I encouraged him to hop on here and let us know what's really going on. He said he would. I'll see if I can pry some more info out of him over the coming days/weeks, though I will have to say that not much has been done yet.

    Anyway, just wanted to make all of you aware of what's in the works. I'll coax him into getting on here tomorrow to give us more information.

  2. #2
    RC Turnbuckle Jr. noir 522's Avatar
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    One word

    LEM
    MAN, Use Common Sense.
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  3. #3
    RC Turnbuckle Jr. noir 522's Avatar
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    Ok well, technically thats not a word. Heck its actually 3 words, formed into an acronym. Or possibly just initials. But anyway LEM differential products are pretty strong already. But ill lend a curious ear.
    MAN, Use Common Sense.
    Outside? THERE IS NO BOX !

  4. #4
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    You have my attention now spill the beans!!!!
    OVERKILL,10Sum,16Sum,Xo1,MMSlas,44Stamp,Rus,16Ral

  5. #5
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    Alright. Let's see if I can shed some light on this bees knees. I am the one spoken of above and I do have some ideas browning in the oven of my mind.
    I'm currently brainstorming ideas for differential and driveline aftermarket options for the Summit. I've found that the stock differentials are simply too small for the truck to begin with and only really high end components manufactured with great precision can hold up for a long time. This is especially true when integrating high wattage power systems into the truck. I can't tell you how many diffs either I or a friend of mine has grenaded due to excessive flex/slop or simply components that are not up to the task. The majority of problems I had were (naturally) while I was running a Tekin RX8/T8 combo in the truck. My slipper was either too loose to have any fun and was always burning up or I was shredding ring and pinion gears. I am familiar with and proficient at shimming a diff too.
    It has also been widely recognized that the stock plastic differential carrier/cup is far to flexible. This is evident in part by the destruction of spider gears.
    I was pretty excited when we started to see aluminum locking diff carriers on the market. I was actually one to own some of the first aluminum carriers to come out of Germany. Paid a good chunk of change for those but they were actually pretty well made. They're still on my truck in fact. Granted, I removed the Tekin RX8 before I put them in and I haven't driven my Summit in about two years; funny how busy life gets. Anyways, I was pretty pleased with those. Tolerances were a bit loose for my liking. Especially the bore for the locking output shaft; way too much slop there. But they never failed on me. Then again, the stock diffs never failed me on the stock motor/esc so that doesn't prove much.
    Anyways, I ended up doing a diff build for a friend who wanted the aluminum carriers as he had had problems with the stock ones. In an effort to save money I looked around online. This was right at the time that the LEM carriers came out on the market. I quickly bought up four, figuring I would make a couple extras to keep on hand. It turns out the LEM carriers are not really anything to brag about. Tolerances seem to be even looser than the German-made ones. The output shaft bore in question was much worse on the LEM carriers. I suspect this is what led to the failure of the rear differential a short time later.

    My friend was a bit concerned and posed the question "weren't these supposed to be bulletproof diffs?"
    Indeed they were. But the aluminum carrier was not up to the task. Mostly due to manufacturing deficiencies. Keep in mind the truck with these diffs was running the stock motor and esc with mudslinger tires. Nothing too crazy there. This is what sparked the ideas behind the potential for improvement.

    The locking differential is a fantastically simple design, but due to small size and average precision, it lives far beneath it's potential. I plan on producing a differential assembly and perhaps steel driveline components from high quality materials, a more robust design and a higher degree of precision. Almost entirely American-made. I confess our shop is not setup to produce gears. I want to be able to shred it up with a brushless system on 6s, drop it into low gear and lock the diffs and not even think twice about hammering the throttle.

    What I would like from all of you are questions, concerns, and a general feeling of how interested you would be in something like this. I realize interest is hard to gauge without any product yet, but I want to know if any of you really want to see this progress. Our shop is very busy right now so it's difficult to devote time to developing my ideas. However, as I complete steps and begin producing parts and running tests I will keep you all posted.

    Currently I'm working on a 3D model of the truck which will simplify the design and fitment process. I'll update with pictures as I can.

    Thank you ladies and gentlemen
    Why can't other people share my opinions?

  6. #6
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    I was hoping to hear you had plans for a larger ring and pinion but I know that would be lots of work. I'm sure you don't want to give away too much info just yet. Could you tell us just what parts you plan to make and from what materials for each? I know Hot Racing makes diff upgrades using softer aluminum. I haven't had any issues with LEM products and am a big fan of their stuff. One of my big concerns would be timing . I have collected 5 Summits in the almost 4 years of being into rc's. Each truck is setup different from stock to 1/5 brushless and most run some type of RC4WD 40 series tires.
    OVERKILL,10Sum,16Sum,Xo1,MMSlas,44Stamp,Rus,16Ral

  7. #7
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    Larger ring and pinion is absolutely in the works. That's essentially the whole point of the project. To get a true 1/8 scale diff in there without losing the locking ability. This was likely going to turn into an entire bulkhead redesign as well. I wanted to end up with a drop in kit that someone could install in thirty minutes to an hour without any dicey modification to the existing bulkheads.
    As far as materials go, I know this might scare some people away, but I'm actually considering the use of steel and stainless steel in key locations, due to some of their desirable properties. The critical part with that is keeping the added weight (if there is any) as sprung weight. That way, there is little effect to handling or suspension response. There are grades of stainless out there that are quite light and yet incredibly robust, not to mention the option for hardening.
    Why can't other people share my opinions?

  8. #8
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    Larger ring and pinion is absolutely in the works.
    ALL I NEEDED TO HEAR .
    OVERKILL,10Sum,16Sum,Xo1,MMSlas,44Stamp,Rus,16Ral

  9. #9
    RC Turnbuckle Jr. noir 522's Avatar
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    Long ago RC Monster made erevo 1/8 sized diffs that dropped right into the stock bulkheads. These were huge and still fit in.
    MAN, Use Common Sense.
    Outside? THERE IS NO BOX !

  10. #10
    RC Champion rizz0d's Avatar
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    the summit really needs x-maxx sized diffs.
    youtube: rizzodtheRCvlogger

  11. #11
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    So what kind of time frame did you have in mind?
    OVERKILL,10Sum,16Sum,Xo1,MMSlas,44Stamp,Rus,16Ral

  12. #12
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    Time frame is looking to be a bit out there. I'm likely not going to even start modeling anything much less producing prototype parts until at least after Christmas. Things are kinda busy right now and I have very little excess modeling and machine time at the shop. Coupled with rebuilding a full-size car there's not much extra time. I will start thinking up some ideas and get them started modeling soon though. If you guys want this to happen I might need you to get on my case and push me for progress. I'll try to get a usable model of at least the rear bulkhead/driveshaft assembly by the first of January. Hold me to it gents!
    Why can't other people share my opinions?

  13. #13
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    Any updates?
    OVERKILL,10Sum,16Sum,Xo1,MMSlas,44Stamp,Rus,16Ral

  14. #14
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    Ok. I stopped by the shop today to see what was up.
    Still being very busy, it seems we might have to wait more. He's got some military obligations or something that are really tying up any free time that he has. He's working on it as much as he can and will hopefully update us when he gets some real progress. But if know this guy like I think I do, he will definitely give us results. I did see what he has so far on the 3D model. I already like how detailed it is. I don't know anything about 3D modeling, but it sure is cool!

  15. #15
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    Oh man reading this just made me a little giddy! Now i still have to say im truely impressed with lem strenth. Yet i did have some tolerance issues. Not being to loose but they were a little to tight. I hade to take a file to the dogbone to make it fit the shaft it slides on. And i had to file both diff cups so the lem spider gears would fit. That being said, i did not have to shim them at all and they are super strong over factory.
    If it still moves, it aint broke enough!

  16. #16
    RC Champion olds97_lss's Avatar
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    Quote Originally Posted by noir 522 View Post
    Long ago RC Monster made erevo 1/8 sized diffs that dropped right into the stock bulkheads. These were huge and still fit in.
    I sent that guy an email last week asking why he quit making them. He said they just weren't up to snuff with the strength he wanted them to be. They were better than stock, but with the size of the bulkhead area, he couldn't put larger bearings on the input shaft, which is where quite a bit of the high power revo problem lies. The bearing takes all the strain and breaks down or gets sloppy which means you have bad mesh and fried gears. He said he milled as much as he could out of the case and eventually started milling down the 1/8th pinion shaft and using a smaller ID bearing as well as a bit larger OD bearing, but he still didn't like it.

    Emails from Mike
    Quote Originally Posted by Mike - RC Monster
    The stock diffs hold up well when using the stock plastic slider drive shafts, but once you add cvds and some traction, they tend to be overwhelmed(especially with 6s). The inherent issue with the Revo is the bulkhead design - it doesn't allow enough room for a suitably strong pinion bearing setup, which was the ultimate weak point in our hybrid setups(still stronger than stock, but not as strong as a similar diff setup in the Maxx truck, which have plenty of room for a big pinion bearing setup). The LST setups work, but require modifying the bulks, which then becomes the weak link in a crash situation.

    The problem is in the bulkhead – there is only 15mm of space, so a 14mm max bearing diameter(must have a case for the bearing to sit in)…an 8x14x4 bearing cannot take the thrust load over time and fails. 8x16x5 bearings are exponentially stronger in their thrust load capabilities, which is why they are typical in the application. Our hybrids used all the available space(a very tight squeeze) – there just isn’t enough space to build a proper setup. I have a v4 90% designed, but it is still a work-around for the core issue of not enough space. The concept of v4 is to use a 5mm diff pinion shaft(Losi 8 for example), which allows a beefier 5x14 bearing to be used – still not as strong as the 8x16 and also uses a 5mm shaft, which is also a strength compromise vs 6mm or 8mm pinion shaft. While I am certain it would be better than stock, I am not convinced it would be as strong as needed for the hard users(and it is a LOT of work to find out).
    Expert rigging at it's best!

  17. #17
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    Hello everyone. Just want to throw a quick update out there. I've been very involved with other machining projects and life events for a while now so the Summit diffs have been forced to take a back seat. However, I tentatively plan on diving back into this project sometime this summer.
    Why can't other people share my opinions?

  18. #18
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    Hello,

    I am interested in good products to strengthen potential week parts. This sounds right up my ally! I just got an old used Summit. I will eventually be upgrading motor and drive components.

    I used to have a Losi Aftershock (LST2) that I upgraded the gearing using the "high speed" kit that was titanium, they seemed very well made and did very well for that application. I'm not sure if those were a nitride coating, but they seemed too light to be steel.

    Anyway, looking forward to learning more.

    Thanks

  19. #19
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    any updates?

  20. #20
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    Quote Originally Posted by bumblebee View Post
    any updates?
    haha, funny you should ask. I'm getting deployed to the other side of the world this fall. Unfortunately, that will put a pause on the work that I've started.
    Why can't other people share my opinions?

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