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  1. #1
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    keep breaking rear differential ring gear /even after shimming

    Hi guys i have a summit with the mamba monster combo and 40 series rock crushers, i keep having issues with stripping the rear diff gear i have gone through 5 in like a month i have shimmed both the pinion and ring gear many times in diffrent ways but some of these gears only last 20 minutes before stripping or chipping a tooth, now i have all stock driveshafts and have never broke one, my front diff has raley had any issues and when it did it was just bearings ,i am getting very frustrated with this if anybody has any ideas on how to take care of this very annoying issue i would be greatful, thanks

  2. #2
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    I have the monster mamba in my summit, and I run 40 series Mudslingers. I was having diff issues and here's what I did. I set the punch control to 100% and turned the power down to 70%. Don't use crawler break, and I have reverse power set to 70%. This is what it took to keep mine together. It's still alot faster and more powerful than stock. Still way more fun to drive than stock.

    NOTErized!

  3. #3
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    Have the same experience!

    I also have a MM Combo in my Summit and also stripped my rear-Diff last week. The Funny thing is that I adjusted the punch control from 80% to 0%

    So New Diff and Punch Control back on!!.

    Also I will be packing between the Diff and Bulkhead out with Polymorph plastic on rebuild.

    .

  4. #4
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    Thanks for replies, what about when you guys are crawlong? I have my clutch set to slip if i get hung up on anything good enough, my punch control is set and 20% lol but still the e revo has the same rimg gear and it comes brushless also and most dont have these issues ive noticed the traxxas gears dont seem vert well made i have a few ring gears here that actually have bubbles in the metal teeth after breaking , ive already orderd twp hardend ring gears from rc damper last week we will see if it holds up, im chipping /stripping teeth even when crawling it really doesnt take much to stip the rear diff for some odd reason, if all else fails il buy all new diff housing also or switch the fronr to rear lol since the front hasnt had any issues

  5. #5
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    My guess is do you need to shim?

    If it's breaking after 20 minutes / 5 per month you have serious alignment issues that's probably not MMM related. I would undo any mods and start from the stock specs.

  6. #6
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    Did you read the title?

    Btw like i said before theres many people running the same set up that havent had any issues, ive shimmed in many diffrent ways ive replaced bearings with play, anything that i thought could be causeing it but i have not replaced the cases yet, that will be my next step and if that doesnt work il drop a losi diff in there and lose the rear locking function im sick of this happening its an rc car we should be able to use them as intended not have to treat it like a crappy fragile toy thats the whole reason i bought it

  7. #7
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    how tight is your slipper clutch?

    I would look at the throttle curve on the ESC and using the graph function on the computer, change it so you dont get that initial shock to the drive train. The front end doesnt get nearly as much abuse as the rear simply due to physics and mechanics. Forward acceleration puts the strain on the rear as the opposite occurs in reverse.....but you already knew that part

  8. #8
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    I will admit my slipper is somewhat tight but its will slip if my truck gets hung up on rocks or trees crawling never blew a driveshaft 1.5years stock, i have been messing with diffrent curves and firmware versions, im going to lower my punch also, and yes when that rear end squats under power there is an enormous amount of force to those gears, lol i try to never punch it and just ease on the throttle but cime on thats not always fun haha , also i never have issues with my spiders, lol my biggest issues with the summit are the bearings, bulkheads and ring gears other than that its bulletproof,,

  9. #9
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    Slipper clutch
    Punch Control
    Self control
    Suspension setup
    Tire selection


    These are all very important aspects of keeping the diffs in check. You cannot buy a $100,000.00 Nissan GTR and drop the clutch at every single red light and expect things not to break. Fortunately these cars are 200x cheaper, and yet still suffer similar problems. It IS a fragile toy that needs to be treated properly, if it was SOLD as a basher and broke this often that would be a problem.

    I agree it is extremely annoying replacing things - especially when you find things like bubbles in the metal - but when you are replacing them on a car that was never intended to do what you're doing with it in the first place, you cannot blame anyone but yourself.

    In order to make it last, set punch control to 100% never LOCK up the brakes from full speed, never have the differentials locked unless you are crawling, make sure the slipper clutch has a bit of play and watch how you land jumps while just generally driving "smart."

    I don't mean for this to sound know-it-all or condescending, but this vehicle is ONLY sold as brushed quite clearly for a reason.

    Threads like this tend to lead people to ever so popular line of thinking, "as soon as you go brushless in a Summit, it breaks!!" When it should be, "as soon as you treat a Summit like an E-Revo, it breaks!" Huge difference.

  10. #10
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    I have not saw the tread on shimming yet. But thre is alot going on there. Its a strigh bevil gear, not hilical like 1:1 are, so alot easer. would have to see the broken gears to give you a idea. If your breaki.g alot and others can make the mm live then you have some problem. Eather inyour gears mesh set up or the case isflexing under load. If its the tip of the pinion (part arossed from where the drive shaft hooks) breakupng off and leaving some or most of the part up against the bearing then the pinion depth is to shallow. If its brewking the the tops (crown) off and still leaving the bottem of the gear (root) of the ring gear. Thats too much backlash.bearing need to be in top shape. Its a ball bearing and not realyy deeinged to take side load. In 1:1 stufff a taperd roller bearing is used. The way a ring and pinon work is they try to seperate under load. In 1:1 stuff alot can be done in like a drag racing.set up. So the pattern (contacts patch) gets better under load, but thwt makes it very weak in reverse. I would start with good if not new bearings and check for cracks of flaws in the case halfs. Make shure all the screws are not striped.
    My posts and summit are a hazard to your health

  11. #11
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    Thanks for replying, i understand what your saying i make sure to never ever lock the front brakes i have drag set for that i also never lock the diffs unless i am stuck crawling ,, but everyone keeps forgetting these are built off e revo platform with the only things diffrent are rhe locking diffs and crawler gear

    , the e revo is made to be fast so why cant the summit do both? I am a mechanic by trade and i know there should not be any form of bubbles in these gears , they are cheaply made man , i have a very good understanding in these things, if you took that gtr and upgraded the drivetrain you could do burnouts at every streetlight lol , alot of people dont rwalize all the summit is, is an e revo with locking diffs lt rockers and second gear,, that is the EXACT same ring gear in the revo to the summt ive had my summit for almost two years and abuse it alot i expect stuff to break its all part of the sport but these diffs arr a known weak point in the summit/revo like i said i think it has something to do with the cases the meshh looks off a bit if the new hardend steel gear strips i will upgrade to a losi diff

  12. #12
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    Suspension im running gmade piggyback shocks best upgrade for suspension ive ever had on an rc,, i agree with gojeep my cases may be flexing, ive had brushless since week 1 went through a few WP SC8 combos then went to a waterproof mamba moster i rarley ever had issues for a full year and now i cant get 3 hours of run time without one breaking, i know the rock cruchers and mmm put alot of stress but id rather have driveshafts break than 17$ ring gears i also have big joes butvthey put just about as much stress as the crushers

    Haha i see ^^^ theres another mechanic

    Anyway il get some pics of a few of the recentvgears
    Last edited by skunkmann; 03-16-2013 at 11:25 AM.

  13. #13
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    The gears may be the same, but the bulkheads ARE different, and when THEY flex they allow the gears to mis-mesh causing the stripping. That's why the e-revo stands up to the abuse better than the summit. If you want you can put the e-revo bulkheads in, but you will lose the locking side of things. The gears that are in the E-Revo will be the same quality as the ones in the Summit, so there's no point in saying the E-Revo is stronger, it just comes down to the bulkheads flexing.

    You said you have drag brake set?

  14. #14
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    Now i think we are on to something, i forgot to ention that my rear bulkhead is broken in3 peices and put back together with aluminum lol no one local has any bulkheads in stock and i drive my summit everyday so it definatly does flex im going to order a bulhead and thegear cases
    The e revo bulkhead is not too much diffrent, if i can lay my eyes on an revo bulkhead i may be able to make it work, but i never said the erevo was stronger i just said the platforms are very similar , and yes my drag brale is set , for soe reason no matter how i programy mamba monster its brakes are always 100% so i just use drag brake instead,, im really not a high speed driver more just alot of crawling and some heneral bashing

  15. #15
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    please bare wih my crappy pictures , i pulled the diff out as soon as itstarted to click yesterday, it seems like the pinion is riding on the very edge no matter how much i shim ,


    in this pic you can see the shiny spots on the pinion where its slipping


    this pic shows the ring gear is still in good condition, there are no flat spots or breks yet

    thanks

  16. #16
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    Quote Originally Posted by skunkmann View Post
    Now i think we are on to something, i forgot to ention that my rear bulkhead is broken in3 peices and put back together with aluminum lol
    you got everyone trying to help you but you leave out this tiny gem... LOL would be an understatement

  17. #17
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    Ah yeah it has to be the bulkhead for sure then, as soon as those gears slip... with any amount of power they will just shred the heck out of themselves.

    I can't get any bulkheads local either - well I just have to wait for them to come in I guess.

    The more grease that's in there, the easier they will slip as well.

    The drag brake isn't bad, I was thinking of crawling brake as in... 300% brake power as soon as you let go of the gas.

  18. #18
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    you're forgetting about rotational mass. those tires are quite a bit heavier and they get heavier exponentially when they start spinning at a high rate of speed. I just weighed a couple wheel/tire combos;

    22oz - Mudslinger 40 series(every other lug removed) on tech 5 rim
    14oz - Stock Canyon w/ beadlock ring
    9 oz - Road Rage (non 40 series) on emaxx rim

    I don't have a stock erevo wheel/tire to measure, but im thinking it's similar in weight to the road rage. I think the rock crushers are just too much for the drivetrain with that kind of power. As for the GTR example, sure you could upgrade the drivetrain, but what would it take for a GTR with 2500HP to handle burnouts and highway speeds on 44" boggers?

    Maybe you can put some erevo tires on your summit, drive it like you normally do, and see what happens?



    nevermind, i just read the part about the busted bulkhead...
    Last edited by rizz0d; 03-16-2013 at 02:29 PM.

  19. #19
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    lol im sorry sometimes i forget about old fixes , haha as im sitting here writing i look down at the case for the ring gear and pinion and realized im a dummy or blind and have wasted 60$ on gears! right at the output shaft where the pinion slides through the plastic is cracked! i thankyou everyone for your help

  20. #20
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    No problem, hopefully someone will come across this one day before spending so much on gears, if anything you're the one who has helped people! =)

  21. #21
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    thankyou krallopian and rizz0d i hope this does help haha , my bulkhead fix is actually pretty strurdy lol, but the biggest issue i have , is i had no issues with my crushers or my oil cooling system weighng my summit down before and breaking gears, shes set up pretty good with the shocks ect, but me missing seeing the crack in the gear case has cost me b
    Last edited by skunkmann; 03-16-2013 at 02:50 PM.

  22. #22
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    wow, im surprised the gears hung on for any amount of time with a crack right there. guess that's another thing to add to our "101 point inspection" whenever we tear it down

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