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  1. #1
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    ~First Time Diff Shim Help!~

    Just looking to see if there are any recent helpful guides on how to shim your front and rear diffs/which size shims go where. Iv already purchased some 6mm, 8mm, and 10mm shims along with some ceramic bearings. As per the inside of the diff(gears and such), would Mobil1 Synthetic grease be good to use?

    Any other information on this would be wonderful

  2. #2
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    Quote Originally Posted by Mr.Cabral View Post
    Just looking to see if there are any recent helpful guides on how to shim your front and rear diffs/which size shims go where. Iv already purchased some 6mm, 8mm, and 10mm shims along with some ceramic bearings. As per the inside of the diff(gears and such), would Mobil1 Synthetic grease be good to use?

    Any other information on this would be wonderful
    this is from the emaxx but the diff are the same so the principle is the same


  3. #3
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    I made shims from a coke can. And it's best to use actual silicone diff oils, I'd suggest 70k front and 30k rear

  4. #4
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    After I shattered both my diffs. I rebuilt them with Hot racing aluminum cups and new parts. I noticed when shiming them I had to use different size shims in each one. I think you have to go by how they feel.

  5. #5
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    So i guess its a no-go on the mobil1 grease?
    I have no hobby shops around so id have to order the stuff online. Would take a while):
    Awesome! Great visual for the differential thank you

  6. #6
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    Anyone know if the grease is a good viable option? or should i strictly stick with the diff oil.

  7. #7
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    Grease won't do anything silicone diff oil is they proper oil to use to tune the diffs.

  8. #8
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    I didn't want to start a new thread so thought I'd post a question here:

    How tight should the screws be tightened down on the cup and gear? Also, how hard should it be to turn. Might feels a bit tight, and it's not even shimmed. I used 60k sil diff fluid

  9. #9
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    Not too tight just until the screw stop without any force. Thicker fluid makes them harder to spin but it should free without binding just the resistance of the fluid.

  10. #10
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    Put the 2mm Allen wrench that came with the erevo in one out drive, and turn the diff gears with it. If you feel the gears meshing too much then lisence all screws 1/4 turn at a time till it's a tiny mesh resistance but fluid isn't pouring out of the diff

  11. #11
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    Does anyone sell the shims in a variety pack?
    You have to pin it to win it

  12. #12
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    U need 6mm shims and 8mm shims. U wana shim the input pinion with 6mm shims and u wana shim the output pinion that goes thru the ring gear with 8mm shims. That will push the ring gear into closer mesh with the input pinion. Also take out any space in the diff side to side. Thats the only two place u need to shim inside the diff. Now on the outside of the diff u wana take 6mm shims again and shim the outside of the input pinion. Where the pinion joins with the center driveshaft. Doing this prevents the center driveshaft from pushing the input pinion inwards and causing a bad mesh.
    Last edited by MotherRocker; 09-07-2015 at 06:15 PM.

  13. #13
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    Can you put this in picture form?

  14. #14
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    This youtube video helped me heaps to understand what needs to be done.

    https://www.youtube.com/watch?v=lQdZnMPPA7Q

    Pictures will not be needed.

  15. #15
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    No, not needed, but helpful! When I rebuild my diffs(With LEM diffcups) I will try to annotate the picture. The video helped me understand how to shim the outside so it wouldn't mesh poorly when pressing the carrier axle into the diff.

  16. #16
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    I will be rebuilding both my diff's this weekend and I can take pics.
    My diffs seem to be okay, but keep leaking diff oil. I believe this is because I have not been able to get a washer on the output gear shaft.
    Do you want pics with the shims in place Kalmlikabohm?

    Mikeorood, I believe that there are variety packs out there with different size shims in it, but I found it hard to find anyone that actually stocked them.
    I just bought 3 different packs of shims in 6,8 and 10mm sized shims. alot easier this way.

  17. #17
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    @Masda, I mean that would be great, but I was going to just annotate the guide mentioned earlier... with color!

    I know each diff/housing can be specific in the amount of shims so I wanted to get a "general idea" before rebuilding again.

    Also, I read that using hot glue between the diff housing and bulkhead eliminates any slop - and does not bond the two together, just pulls off when you need to disassemble.

    @Mikeorod, same. I have just bought 6,8,10mm shim packs from separate sources.

  18. #18
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    Do you shim when the vehicle still new?

  19. #19
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    Quote Originally Posted by jvinhj240 View Post
    Do you shim when the vehicle still new?
    Most of the times it isn't necessary out of the box. The space/slop (that needs to be shimmed) comes from driving the car.

  20. #20
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    I have shimmed mine only after a few runs, other Wise as mentioned above, normally out of the box it would not be necessary.
    Live life to the fullest

  21. #21
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    @kalmlikabohm I did both my diff's recently. I did the front diff over the weekend and the rear one on Tuesday evening.
    I went **** and also cleaned out the ball bearings and greased em up. got to bed after midnight on Tuesday and still paying the price today. Feel soooooo tired.
    On the bright side, both my diffs have now been rebuilt properly and shimmed while I was at it. I would have taken the appropriate pics, but I was too tired to even think about pics.
    The closest I can provide to a stripped down diff and ball bearings is this:

  22. #22
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    Wow, that is a cleaan diff.

    Awesome. I will be re building my rear diff because it moves about 2mm.

  23. #23
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    Brake cleaner fluid does wonders. Just keep it away from the seals and the bearing covers. it will melt if you leave it in brake cleaner for too long.

    The ball bearings were greased up to try and keep he dirt and pebbles from getting into the bearings. They had never been clean and wouldn't move freely at all due to all the much in there. hopefully now they will last longer. A cheap item I know, but I have spent enough money on this beast. The minister of war and Finance in the house is not impressed.

    when you say that the rear diff moves about 2mm, are you talking about the whole diff case, or you talking about the input/output shafts?

  24. #24
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    I've heard brake cleaner will work. I've also heard that you can just ultra sonic the whole thing in any solvent really. Isopropyl alcohol is pretty cheap.

    The whole diff case moves around with 2mm or so. I've read that you can combat this while using hot glue/something to suck up that space. The hot glue will not bond and just creates a near perfect wedge - or so I am hoping when I rebuild the rear.

    My front does not move but the bulkhead is cracked #it'sAlwaysSomething.

  25. #25
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    What size is the o-ring?

  26. #26
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    Which oring?
    Quote Originally Posted by Supamegaman View Post
    What size is the o-ring?

  27. #27
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    Quote Originally Posted by Mr.Cabral View Post
    Anyone know if the grease is a good viable option? or should i strictly stick with the diff oil.
    The diff is separate from the differential carrier. The diff is the combo of the ring gear and pinion as well as the diff carrier(the cup that holds the spider gears and bolts to the ring gear)and has 2 case halves that bolt together.

    The carrier is a cup that holds the spider gears together and is sealed off from the diff housing which holds the ring and pinion and is bolted to the ring gear. This cup/carrier attaches the axle to the ring gear via the spider gears.

    In the carrier you need a fluid/oil to keep the spider gears lubed properly. The carrier has a silicone O-ring seal at each end to prevent oil from leaking out through the axle.

    In the diff case for the ring and pinion you can and should use grease to lube the ring and pinion, because if you don't any oil will flow out of the joint between the 2 diff case halves and leave the ring and pinion un-lubricated.



    Now here is one interesting point to consider when choosing what oil to fill your carrier with.

    The silicone O-rings are compatible as far as I can tell with basic conventional petroleum based oils.

    Ball Bearings will wear out prematurely if exposed to silicone lubricants!

    So if your silicone oil filled carriers leak out, the silicone oil will flow out through the diff housing and in the process wipe out your bearings which will in turn wipe out everything else inside the diff!

    I realize that I may receive back lash for this suggestion but I am running conventional petroleum based gear oil(SAE 80W-90) in my carriers. I have pulled them apart several times for various reasons and have found that the oil has remained in the carriers with out leaking out and has not had any adverse effects to the silicone O-rings so far. I also have filled my shocks with the same results. I have noticed a much improved performance from my shocks however as silicone oil is not a hydraulic fluid and shocks require a hydraulic fluid to function properly. This is just my opinion and should be taken with a grain of salt!

    Also the silicone O-rings can be replaced with rubber ones if you feel uncomfortable with using silicone O-rings with petroleum oil.

    If you use petroleum oil in your carriers. In the event that the carrier leaks out, the petroleum oil will then leak out through the diff bearings and actually properly lubricate everything in the process, and will mix well with your petroleum based grease used on the ring and pinion. Aside from the obvious mess it will leave lol it will cause no harm to your components. However, the same can not be said if you use silicone oil in your diff carriers.

    I use a petroleum based grease on every gear to gear contact on my E Revo except for the spur and motor pinion gear. Petroleum based grease will not wipe out your bearings but silicone grease will!!!

    I would avoid any petroleum based grease or oil with additives or detergent in them tho just so there is no adverse effect with the silicone rubber seals.

    Also remember that not using the recommended fluids will void any warranty !!!

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