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  1. #1
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    Talking NA`s Diff Shimming Guide

    I`d like to start by saying this is only how I shim my diffs, many other people have different methods. To each their own. As shimming is kind of an art all by itself, that's why there aren't really any definitive guides for shimming, its different for each truck.


    These are the shims and o-rings I use.


    I like how these 3racing packs have multiple thicknesses of shims in the same package.
    Last edited by Northern Adventurer; 12-05-2013 at 11:05 AM.
    To SUMMIT up, its my coolest RC.

  2. #2
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    With that being said, here is where I start, a pic-by-pic disassembly guide, perform the same in reverse for assembly:










    To SUMMIT up, its my coolest RC.

  3. #3
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    That concludes the disassembly, please perform the same in reverse for assembly procedure. See how dirty the oil was?



    These parts have been rag wiped to remove most grease prior to proper cleaning.

    One of the second cups outputs needed a little coaxing to come out lol


    Both diffs rag wiped prior to proper cleaning.


    Here Im taking note of where shims were.
    To SUMMIT up, its my coolest RC.

  4. #4
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    Then collect all the metal bits in a jar for a real cleaning with brake cleaner.


    Everything fully cleaned.


    Ready to dry assemble to test for shimming.


    Continue assembly.


    Here I am wiggling the output to test for how much shim room will be needed.


    Here I have placed shims on the output to be reinserted and tested again. What you are looking for is to be as tight as possible without binding.


    Don't forget to use all rubbers when dry fitting.


    There is now no slop with the shims.


    Then do the same testing/shimming/dry fitting with the other output.

    To SUMMIT up, its my coolest RC.

  5. #5
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    This diff cup has now been properlly dry shimmed and hand turn tested.


    Now on to shimming the cup into the housing.


    You can test fit everything to see if shimming is necessary.


    I ended up shimming one side between the ring gear and bearing. This brings the ring and pinion closer. Once agian, dont shim to tight.


    Shimming this bearing on the other side can also be done if needed, Was not necessary for me.


    Finish dry assembly.


    Hand turn test to check for tightness/binding.


    Here I needed more shims to bring the pinion and ring gear closer, You may need to dry assemble and disassemble many times in order to find the perfect combination.



    CAUTION:
    Once fully dry assembled, you must attach the axles to ensure they can still be attached. It is possible to over shim, when you over shim a diff, the holes for the screw pins on the output can no longer be accessed because they have been shimmed too far into the diff itself.
    To SUMMIT up, its my coolest RC.

  6. #6
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    It's been ALOT of work, You are ready to disassemble and reassemble with fluids.


    I grease the o-rings on the outputs.


    Insert it.


    Fill the cup half way with your desired fluid, I use 120k in the summit, stock is 100k. Then insert the spider gears, top off the top with diff fluid again, then screw the ring gear on. Leave one screw out for last so excess fluid can pour out.


    Assemble into the housing, and your done the diff.


    Then I assemble the bulkheads with the diffs in them.




    I then hot glue the inside of the bulkheads for added strength, keeping dirt and crap out and to eliminate slop in the bulkhead.


    Its easily removable, just peels off.


    This concludes my diff shimming and gluing thread.

    Please remember this is not an exact science, more of an art form. This is only how I do it, everyone has their own methods.

    I just wanted to share my method because I found it very hard as other do, to find guides on this.

    I hope this has helped some of you.



    For Dennis.
    To SUMMIT up, its my coolest RC.

  7. #7
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    Excellent write up and pics!
    This is how I do it as well. The hot glue is very important in my opinion, my diff's last a lot longer now.
    As NA stated, don't over shim, dry test then test again. Take your time and you will be rewarded with an efficient long running diff.
    NA, all you need now is for LEM to make a billet diff cup housing lol. Those are REALLY nice looking diff's and axles. I'm jealous.
    Wish I didn't have so many hobbies spreading my cash thin, sportbike just cost me $2500 for some cool mods

  8. #8
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    Thanks, Im glad Im not the only one doing it this way.

    LEMs parts have been very good to me, They may already be working on the model/prototypes for the housing... Shuhhh...
    To SUMMIT up, its my coolest RC.

  9. #9
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    Wow nice job. The photos really help. Havent tried to do this yet but when I do this will guide me through. Noir522 should include this in the FAQ section. Its that good. Thanks for taking the time and sharing with us.
    "Better Old and Devious than Young and Exuberant"

  10. #10
    RC Turnbuckle Jr. rag6's Avatar
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    Thanks for posting 8)
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  11. #11
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    Thank you for taking the time to post this, being "new" to diffs etc, this is extremely helpful.
    Summit 1/10th | Mini E-Revo VXL |

  12. #12
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    Thanks guys, Glad to know it may help some out.

    I can always help with anyone who has questions I may not have covered, as im sure I missed a few things.

    If anyone has any other tips and suggestions for shimming, please feel free to add them in.
    To SUMMIT up, its my coolest RC.

  13. #13
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    Excellent tutorial! Gonna bookmark for the next teardown.

  14. #14
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    Great stuff NA
    Working hard to appear reasonably sane.

  15. #15
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    Is it necessary to shim the diffs from day 1, or should you run the truck a bit to wear them in before hand?
    Ya can't polish fertilizer...

  16. #16
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    Not necessary, I didn't with my summit when it was new... buts that's cause I didn't know how.

    I did from new with my e-revo and have never broke a tooth yet...

    I recommend from new if you have the knowledge/ability.
    To SUMMIT up, its my coolest RC.

  17. #17
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    Hey NA, what size shims did you use? 5mm 6mm and 8mm?

  18. #18
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    Great write up thanks.

  19. #19
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    Outstanding job NA

    Needs to be pinned F&Q section Noir.
    Endeavoring to persevere !

  20. #20
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    LEM Alu cup problem

    Hi,
    I'am working on my differentials and when i screw the main gear all the way to the aluminum cups, the gears inside the cup block and won't turn anymore.
    What am I doing wrong ?
    Thanks for your help

  21. #21
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    NA`s Diff Shimming Guide

    Turn them a little as you tighten them evenly,to make they mesh and seat correctly.could also be the I bar is not seating all the way down.
    If you used shims maybe need to remove one

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  22. #22
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    The " I " bar is directional as well one side will have flats on the end and other side comes to a semi point.

  23. #23
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    Hey there northern...What r u using for o rings? Is that just an o ring out of a o ring kit? Is there a need to shim if it's all stock?
    Drive Angry My Friends!

  24. #24
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    Quote Originally Posted by smogutator06 View Post
    Hi,
    I'am working on my differentials and when i screw the main gear all the way to the aluminum cups, the gears inside the cup block and won't turn anymore.
    What am I doing wrong ?
    Thanks for your help
    I ran into this same problem just a few days ago when I was building my LEM diffs. Its the Ibar that is your problem.

    Check out your thread on LEM's site, I posted a little more info about it there.

  25. #25
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    Thank you for this!
    Slash 2WD, Slash 4WD, T-Rex 250
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  26. #26
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    Thanks for the info it's helped alot.

  27. #27
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    What size shims do I need for this?

    My buddy just blew his rear Diff. So we are installing a new stock Diff and want to shim it so it will last longer.

    I also need to tear mine down and shim it.

    Thanks!

  28. #28
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    Quote Originally Posted by Badmunky View Post
    What size shims do I need for this?

    My buddy just blew his rear Diff. So we are installing a new stock Diff and want to shim it so it will last longer.

    I also need to tear mine down and shim it.

    Thanks!

    6mm for the diffs. 8 and 10mm for the ring and pinion.

  29. #29
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    Quote Originally Posted by LeadingEdge View Post
    6mm for the diffs. 8 and 10mm for the ring and pinion.
    Thank you!

    I plan to build some new diffs with LEM parts.
    I just hope the new diff housing is released soon!
    I'm kind of waiting for that before I order all the stuff I want. For now I just plan to shim me stock diffs to get a little more life out of them.

  30. #30
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    Shims are the life of the diff. IMO

  31. #31
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    That they are!

    Mine are shimmed. But they have well over 100 runs on them at this point as its time for fresh fluid and a reshim.

    My buddy never shimmed his. He got well over 300 runs in before the rear diff failed tho. So I think he got lucky and got a truck that did not really need shims when it was new.

    I just want my stock Diffs to last long enough for the new LEM Diff housing to come out. That way I can build a set of bomb proof Diffs with LEM housing and Diff cups/gears!

    Plan to put in all new ceramic bearings at the same time.

    Just need to figure out what I want to use for the ring and pinion gears still.

  32. #32
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    I may be wrong in my thinking here if so I'm sure everyone will let me know. Ceramic bearings are not ment for high impact situations such as the pinion gear. They are more ment for high speed and less friction . After all they are basically made of glass. That's why I never used them in the diffs to start with.
    OVERKILL,10Sum,16Sum,Xo1,MMSlas,44Stamp,Rus,16Ral

  33. #33
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    Quote Originally Posted by Badmunky View Post
    That they are!

    Mine are shimmed. But they have well over 100 runs on them at this point as its time for fresh fluid and a reshim.

    My buddy never shimmed his. He got well over 300 runs in before the rear diff failed tho. So I think he got lucky and got a truck that did not really need shims when it was new.

    I just want my stock Diffs to last long enough for the new LEM Diff housing to come out. That way I can build a set of bomb proof Diffs with LEM housing and Diff cups/gears!

    Plan to put in all new ceramic bearings at the same time.

    Just need to figure out what I want to use for the ring and pinion gears still.
    The stock Traxxas ring and pinion gears are a lot stronger then you think once they are in something that doesn't flex.

  34. #34
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    Hmmmm now if we just had a diff housing that didn't flex oh say made of 7075 aluminum
    OVERKILL,10Sum,16Sum,Xo1,MMSlas,44Stamp,Rus,16Ral

  35. #35
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    What a great guide! I will definitely go through my diffs and I've already ordered 6, 8 and 10mm shims. I will order the diff cups as soon as my finances are in order, and one would hope to find som *ahem* 7075 housings as well soon
    Summit, Stampede 4x4, Slash 4x4

  36. #36
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    Sorry to comment on a old post, the shims for the output gear on the locker side, are these the 8mm shims cause the 6mm shims won't fit? Trying to shim my lem diffs to get rid of the wobble. Thanksp

  37. #37
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    I ordered some 3racing 7mm shims for that side. Integy stocks em.

  38. #38
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    Awesome write-up! Worth the bump

  39. #39
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    When you are assembling / changing gears in Land Cruisers ( maybe aplicable to other brands but I can talk about my experience which it's on Cruisers ) we use R&P marking paint to see the matching contact between ring and pinion and according to that contact pattern define the shims .. here it's just with the idea of making the all setup as tight as possible without binding .?

    How loose it is from factory ?

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