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  1. #1
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    issue with rear diff in mmm2 EMaxx

    Just got done building a EMaxx from the ground up. Flm chassis, rpm everything, steel cvd's, waterproof everything, savox servos, cc bec, trenchers. I have shimmed the diff's and run the truck to and blow the rear diff then found out i did not shim the pinion and it slammed into the ring gear. So I corrected that problem, diff seemed perfect wasn't hanging up and seem tight. Ran it a second time to do the same thing but I blew a brand new bearing holding the pinion. I am running gon a 4s and my understanding is I shouldn't be having so much of a headache bout it.


    I looked into doing some avid bearing's and if the issue still happens then when funds come available I'll break down and buy some hybrid diff's to accommodate those 1/8 diff's. Any advice to what I may be doing wrong would be appreciated it. I got way to much in this truck to be having something in the drive line causing me a hick up.

  2. #2
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    Loosen the slipper a little so that it absorbes some of the torque and dial in some punch control (need castle link for that). Your truck is a good bit heavier now and that diff is going to have a hard time surviving. Hybrid bulks and 1/8 scale diffs are in your future.
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  3. #3
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    Ya I started messing with the punch control seemed to help some but would it be worth it to do aluminum cups and cases or just wait and do the hybrids? I have two questions about the hybrids. I assume buying the ultimate they come with everything needed and just a bolt on correct?? Maybe need shims? If I do the hybrids will I have to do both front and rear? And my last question, I also assume running the hybrids will solve my while issue??

  4. #4
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    The hybrid bulks will solve the issue, but you have to source your own diffs. I am going to use the diffs from a vorza flux 8th scale buggy.
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  5. #5
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    Well the ultimate combo includes a diff from flm. I believe it is simply a bolt on but again I'm sure there is some shimming involved. The hybrids sell $70 and the ultimate combo $90 so not much more then you get the diff too.


    Would the two hybrids have to be done at the same time or could you do the rear and then the front later??

  6. #6
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    the problem is that these parts are not in stock with FLM. I got my hybrid bulks with no diffs from ebay and then had to order the diffs separately.
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  7. #7
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    Im fairly new to this and have only blown one diff but I replaced it with a spool for $12 to get rid of the spyder gears and lock it up. It works very well. I run 4s with steel CVD's as well and Im surprised you're having that many issues.

  8. #8
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    You can get the hybrids bulks and ofna hyper 7 diffs. If the diff is shimmed properly it should last..stock ones never gave any issues. Also you can use the punch control on the esc to reduce stress on the driveline.

  9. #9
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    The first time I blew it cause I did not shim it right but I fixed it and the second time I blew a brand new bearing. I am willing to order the hybrids from rc monster or who ever and wait for them to make the parts but doing those and then adding ofna diff's is just to much money. I haven't heard of many ppl have my issue on a 4s but maybe with the big tires and flm chassis I could be putting a strain on the drive train idk.

    Running the hybrid diff's, can you still use the stock traxxas steel cvd's? And use the erevo drive cups??
    Last edited by cooleocool; 04-30-2014 at 08:42 AM. Reason: merge

  10. #10
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    I'm having bearing issues with my front Diffs constantly. I have 70% torque/punch limited, 4s, RR slipper clutch, but still is wreaking havoc on the bearings supporting the pinion gear(the little diff bearings). The bearing fails, the spur and pinion get destroyed due to the slop in it when bearing fails. Q: when you guys refer to diff shimming, could you elaborate on that process, I may be missing something?

  11. #11
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    I just replaced the rear diff for the third time last night and had a test run. Seemed to hold up as its the first time I got a full run.


    Shimming the diff is making the mesh between the ring and pinion tighter. And my biggest problem was after the diff was in the truck the pinion had so much play it would slide back and forth slamming into the ring gear causing the issue I believe your having. Which then blows the bearings. So you also need to shim the drive cup on the pinion to keep it from moving back and forth. I do t know where the thread is but if you Google how to shim a maxx diff you should be able to find the thread. I followed it and so far it has worked. Its pretty detailed on how to do it.

    I also moved my punch control to 80%, and slightly loosened the slipper. I'm running the RR gen3. One guy on here said the torgue limiting feature works better than punch control but I haven't played with that yet.

    Hope this helps bud!
    Last edited by BuGgYbAsHeR.28; 05-25-2014 at 09:05 AM.

  12. #12
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    +1 on the torque limiting over the punch control.

  13. #13
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    Busted a pinion today, run number six but the diff's seem to hold up strong so far! I'm using the RR gen3 slipper and now I think its time for a RR pinion.




  14. #14
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    Are you running a metal spur gear too? Seems like the plastic spur would go first.
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  15. #15
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    No the spur is steel. Robinson racing steel spur gear with gen3 slipper. Nice setup

  16. #16
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    the metal spur is probably what cost you the pinion.
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  17. #17
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    Quote Originally Posted by rock-rod View Post
    the metal spur is probably what cost you the pinion.
    +1, that's why RR recommend to use their pinions with their slipper.

  18. #18
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    Yes use both RR gears only, very durable!

  19. #19
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    12.6 pounds with the batteries!! I'm not sure what the stock emaxx weighs but this doesn't too much more if I had a guess. I have RR pinion gear on order with VG racing heavy duty springs, the truck seems to bottom out to easily for my liking. If that doesn't work, any suggestions for cost effective shocks?



  20. #20
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    UE shocks works pretty good, I run 1/8 buggy shocks on mine.

  21. #21
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    Blew a bearing today, I think I'm on a hikd now till I do those hybrid diff's unfortunately.

  22. #22
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    sounds like it. Thats a lot of weight for those 1/10th diffs to support.
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  23. #23
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    Well I have the new RR pinion and some heavier duty springs. I should be ordering the flm hybrids by the end of next weekend and maybe a few weeks to get some more funds for the diff's. Hopefully will complete the build for a while so I can have some fun!!

  24. #24
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    BuGgYb
    I would love to know how the FLM's workout, I have similar parts on my truck and I'm constantly blowing the
    Traxxas 5117 bearings in the diff, which in turn ruins the pinion and spur (Traxxas 5379) in the diff. $25 every rebuild!! I keep plenty of the Traxxas bearings (#5117) and diff rebuild kit (#5379) on hand at all times that's how ridiculous this is becoming!! Ready to quit, we have three of these 3908 E Maxxes and constantly going through diff issues and its always bearing failure which in turn ruins the gears in the diff. Tired of taking them apart only to have it fail after a few runs. I've talked with Traxxas personnel on various occasions and they always point blame at the user? Yeah I guess it couldn't be an inherent design issue?

  25. #25
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    It's a bearing issue. The small bearings are no match for the bearings used in the 1/8 scale diffs. They are much larger and can withstand the torque. Flm hybrid bulks plus vorza diffs is a winning combination.
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  26. #26
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    Ya I def will! But I have done my research and I read so much on the flm's and 1/8 th diff completing the drive line issues. I will try to get my hands on some next weekend so I'm stoked!!

    But I'm not doing the vorza diff as I don't want to have the spiral pinion and just use the hyper 7

  27. #27
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    Rock Rod
    is the FLM complete diff & bulkhead in one a good combo for durability? Also, i read where you cannot buy direct, so who carries the FLM product line?

  28. #28
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    So far it's been durable for me with the vorza diffs. I got my hybrid bulks from ebay. I think you can get them from unlimited engineering or kershaw designs. Diffs that work are Vorza flux, ofna hyper 7, 7.5 or 8, Hot bodies, and there may be a few others. Ofna hyper 9 will not fit. LST2 diffs will fit with some grinding inside the case half, but the pinion is a little on the short side so it's hard to get a good contact pattern. There is another trick that allows you to keep your bulkheads by installing the complete LST2 diff case and gears. It takes some work with a dremel to make some adapter sleeves but the end product works nicely too.
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  29. #29
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    Hey what bearing size is used for those hybrid bulks? And I have the lungsford pins and its my understanding that the bottom pin is different in size so I won't be able to use my Ti ones??

  30. #30
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    8x16x5mm IIRC
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  31. #31
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    Some of you guys are talking about setting punch control. I had spoken with Castle and they said the Torque setting is a better way to go rather than punch control IMO it is much better easier on take off and drive line. Just takes a little time to do. Here is A thread and info on how to set up torque control. Just trying to help.
    http://traxxas.com/forums/showthread...limiting-today

  32. #32
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    How do I know the Hyper 7 Diffs will work? I bought 2 Diffs to go in my FLM hybrid bulks and the Hoboa Diffs I got are too large in diameter 43t gear. What exact diff will work, I do not want to waste another $100 on two Diffs that do not fit! Again I have the FLM hybrids already but need the Diffs, please advise.

  33. #33
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    I was informed that the hyper 7 diffs did work. I was going to purchase those this weekend so I would like an answer as well. I just purchased the hybrids so I had an eye on those hyper 7's. I would like to add and ask if by cutting the 5454 axle studs is a replacement of RC monster's out drive shafts? Can someone confirm that too?

  34. #34
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    I know that lst2 or hyper 9 diffs do not work with the hybrid bulks. Hyper 7,8 or 8.5 will work and also hpi vorza flux diffs will work. I am running the vorza diffs now. The center shafts are a challenge with the vorza diffs. I am running a Traxxas erevo front steel cvd to run the front wheels and a combination or hyper 9 driveshaft with the flux pinion cup and revo drive cup to turn the rear tires. It's possible to use the Traxxas emaxx steel rear center shaft for the rear but will require redrilling the trans output shaft a few mm further down the shaft.

    And yes cutting the 5454 stubs works in place of the rc monster ones. My hybrid bulks came with the stubs though. Did yours?
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  35. #35
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    I'm not sure I just ordered them last night off eBay, guy only has a few left for those looking for them now. I should have those this weekend and hopefully they do like yours did!


    I have the erevo drive cups and using flm's center shafts, would that combo work with using a hyper 7 diff?

  36. #36
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    And also could you list the shims needed for the diff to do a proper shim job rock-rod. Much appreciated bro!

  37. #37
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    order up a set of 8x16 shims in various thicknesses. You shouldn't have to shim the cups but the pinion may need some work. At least with the vorza diffs, I didn't add any shims to the cups at all.

    I don't know what size the pinion is on the hyper 7s so if the drive cups are not included you will have to order some.
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  38. #38
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    So ya rock-rod those hybrids came with the stubs. That's a nice lil bonus. I now have 2 questions concerning the bulks.


    Here are stubs and which I assume 8mm cause I haven't opened yet.




    In this pic, where does that long screw go as there is only one per bulk.?

    Second, where do those lil pins go, there is two per bulk. Is it like a positioning pin or something??

  39. #39
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    Those pins are dowels that go into machined holes in the case halves. They are to keep the halves lined up properly. I used one in the top position screw hole to leave clearance for the shock towers. You will see what I mean when you mock the parts together. Those stub shafts need to be swapped into the new diffs.
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  40. #40
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    Okay that's what I figured. Where does that screw go? It is way longer than the rest and there is only one.

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