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  1. #1
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    Alloy Diff Cups - To shim or not to shim?

    I'm about to put some alloy diff cups and hardened gears into my Summit.

    Would the general consensus be that shimming is still as important as it is when using plastic diff cups or considering that theoretically there should be less to no flex in the cup has anyone experienced that shimming has caused failures? I ask this because I would be the noob who will over shim and create too much pressure on the gears if that is at all possible..

    thoughts?
    another Dewalt...another frequently broken Summit.

  2. #2
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    The idea of shimming the diffs is to bring the pinion and the ring gear closer together so it doesnt wear as fast, being in Australia like me how much did it cost you to do both diffs with aluminium cups and hardened gears and where from?
    Slugs are just naturally aspirated snails

  3. #3
    RC Turnbuckle Jr. jamann's Avatar
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    Quote Originally Posted by SUMMIT51Z View Post
    I'm about to put some alloy diff cups and hardened gears into my Summit.

    Would the general consensus be that shimming is still as important as it is when using plastic diff cups or considering that theoretically there should be less to no flex in the cup has anyone experienced that shimming has caused failures? I ask this because I would be the noob who will over shim and create too much pressure on the gears if that is at all possible..

    thoughts?
    Shim it, it only helps.dry fit it a few times to make sure it moves freely and is not binding.each one is slightly different,So there is no rule exept try to get the shims even on both sides so you don't put anything out of alignment


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  4. #4
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    cheers, will do.

    Joel, roughly the cost of the cups delivered a few weeks ago was $143 and the gears were about $80. I got them from seperate places (Germany/Honk Kong) but only just realised the gear sets are for a Revo and not a Summit so both axle's are the same length. I am hoping I can use the hardened R&P, spiders and 1 axle with the longer Summit axle.

    I'll be doing it tomorrow then flogging it all day Sunday (if it lasts) so will advise outcomes.
    another Dewalt...another frequently broken Summit.

  5. #5
    RC Turnbuckle Jr. jamann's Avatar
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    Yes spiders,ring and pinion and one output are the same between revo and summit.cup is different and the locker output and locker gear are different.


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  6. #6
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    Yea you have to shim even with the aluminum cups. I just did mine, the front required 1 shim. But the rear had so much play that it required 3 shims ( brand new cups/ brand new gears)

    I think we are following the same footsteps ( Germany, honk Kong, one side longer out put shaft, shimming) while I was in there I stuck in some thicker oil/ grease as well. Don't want to have to go into the diff again any time soon.
    Last edited by noir 522; 04-26-2013 at 01:36 AM.
    MAN, Use Common Sense
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  7. #7
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    look like I'm on the right track then, cheers.

    Noir, was there any problem with using 2 different manufacturers axles/output shafts? This is the only thing I am hesitant on.
    another Dewalt...another frequently broken Summit.

  8. #8
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    none that you have not already mentioned, I had to use the longer stock summit axle on the locking side. It fits and turns ok. My fear is that I have often heard that metal gears of two different hardnesses may lead to premature wear (the diff oil should help). But we will see.
    MAN, Use Common Sense
    Funky Gecko, SumVee HDE

  9. #9
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    that we shall, cheers. If it makes it through what I have planned as a shake down run tomorrow then I will be happy with that for now.
    another Dewalt...another frequently broken Summit.

  10. #10
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    hey guys bringing up this thread to ask a question involveing this topic

    what company/part # are the shim packs used for the summit diffs?
    and are there shims to go inbetween the hex hub and axle carrier?

    thank you guys
    summit /mustang /stampede-2s spc lipo

  11. #11
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    Quote Originally Posted by jamann View Post
    Shim it, it only helps.dry fit it a few times to make sure it moves freely and is not binding.each one is slightly different,So there is no rule exept try to get the shims even on both sides so you don't put anything out of alignment


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    This is exactly the way we setup do our cups at lem. Even though our cups are made by precision cnc machines,
    Some require different ammounts of shims.

  12. #12
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    If it fits, SHIM IT. As, others have said, dry fitting is key. Try one shim, dry fit, if it fits try more until you bind then remove the last shim that made it bind. I find if there is a very slight amount of binding its perfect. once you do 1 run the gears will no longer bind and be meshed properly.

    With aluminum cups the I-Bar issue was large issue with some manufacturers, some have fixed the situation Ive changed many diffs over to aluminum cups and found that you need many i-bars on hand to find one that best fits as the stock i-bars have large tolerance differences between them.

    To SUMMIT up, its my coolest RC.

  13. #13
    RC Turnbuckle Jr. jamann's Avatar
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    I have changed a few myself...lol



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  14. #14
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    Quote Originally Posted by jamann View Post
    I have changed a few myself...lol
    Nice pile.
    To SUMMIT up, its my coolest RC.

  15. #15
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    Quote Originally Posted by reod12x2 View Post
    hey guys bringing up this thread to ask a question involveing this topic

    [SIZE=4]what company/part # are the shim packs used for the summit diffs?[/SIZE]

    and are there shims to go inbetween the hex hub and axle carrier thank you guys
    thank you guys for the pic's and info. but what are the part numbers for the required shims to shim up the diff??
    summit /mustang /stampede-2s spc lipo

  16. #16
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    I use 3 racing. I have most of their sizes. not sure on part numbers. 8mm I think.
    To SUMMIT up, its my coolest RC.

  17. #17
    RC Turnbuckle Jr. jamann's Avatar
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    I used 3racing shims as well
    Here is a pic. that pic is not the part # you want.you are looking for 3rac-sw6 (6mm) and sw7 (7mm)
    You get three thicknesses per pack

    6mm for all outputs except the locker output that is 7mm




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    Last edited by jamann; 07-25-2013 at 07:03 PM.
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  18. #18
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    not the exact same differential but they both most parts are identical
    (from RC-Fan)

    MAN, Use Common Sense
    Funky Gecko, SumVee HDE

  19. #19
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    okay thank you guys

    just got around to fideling with the dry diff and all the one needs so far is a couple 6mm shims for the pinion gear.i dont know if its going to be the same for the seconed diff or not .i havent got around to cleaning it out the grease.....not going to worry about the diff oil cuase of the spider gears rubbing against both the cups wall.
    then again shiming is going to be erelivent for quight some time untill i get power back up to 100%.since i will be runing on a single 2s lipo

    but ya thank you for the help and recomendations.
    summit /mustang /stampede-2s spc lipo

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