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  1. #1
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    New to shimming the diff and need advice

    I never really had the need to shim the diffs on my T-Maxx 3.3 since I never really went through that many of them but now with my E-Maxx brushless I feel I'm going through way too many of them and they aren't lasting as long as I think they should. I read a bit on how to shim them but have a few questions. What exactly aim I aiming for? I know that the I need to place a shim on the pinion gear to move it closer to the ring gear but what "feel" am I trying to get to? I know that if the pinion is all the way out and I turn it I feel absolutely nothing, very smooth but the second I push it inwards I feel the pinion making contact with the ring gear and as I turn it I feel it like a slight grinding, and obviously if it's too close to the gear I can barely turn it. So feeling the slight "grinding" is what I'm shooting for?

  2. #2
    RC Qualifier ausprime's Avatar
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    You are looking for a smooth feel to the gears.
    Sometimes it's smooth except for one tooth. If its like this, its all good. That one tooth will wear in to match the rest of the teeth.
    Notice there is an O-ring that goes between the pinion drive cup, and outer pinion bearing. This will stop the pinion from sliding in and out.
    The 8mm and 10mm shims, will stop the diff from moving around inside the diff cases.
    The 8mm shims will raise the ring gear, bringing it closer to the pinion.
    The 10mm shims will go on the other side of the diff, to make the diff a snug fit inside the cases.
    When installing the 8mm and 10mm shims, install the diff, but not the pinion. And test to see if the diff has any side to side play inside the cases. 0.1mm of play is better then no play. Because you don't want to put any side load onto the bearings. Once you're happy with the amount of play, you can then test it with the pinion. If it binds up with the ring gear, take out the 8mm shim from under the ring gear and add a 10mm shim to the other side. Then test the pinion again. If there is to much slop between the pinion and ring gear, add a 6mm shim between the pinion and the pinions inner bearing, and retest.
    You will have to assemble and disassemble a few times to get the perfect mesh.
    Hope this helps.
    If you can get a good mesh they will last a lot longer.
    But they are still weak diffs.
    I would recommend upgrading to 1/8 scale diffs. this can be achieved for about $200 (diff and diff cases).
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  3. #3
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    I don't have an o-ring on the pinion. I have just the two bearings or do you mean add an o-ring because there isn't one on stock? Unless I just haven't noticed it

  4. #4
    RC Qualifier ausprime's Avatar
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    There isn't one from stock. There are no shims in a stock Traxxas diff. But adding them helps. It doesn't have to be an o-ring, normal 6mm shims will work.
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  5. #5
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    I gotcha. Do you know if places like Lowes or Home Depot have them?

  6. #6
    RC Qualifier ausprime's Avatar
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    I buy my shims from AMain hobbies
    http://www.amainhobbies.com/search?s=shims
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  7. #7
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    What happens with the stock diffs, is there is also flex in the plastic when under power. So this moves the gear mesh apart slightly causing a misalignment. This is what breaks them. Shimming helps to kind of preload the gears to keep them in place better.
    On my E-revo brushless edition I was having the same issues, I replaced both the diff cups and housings with all aluminum along with shimming them. I have yet to really beat on them hard, but now there is no more flexing in the housings so in theory they should be stronger.

  8. #8
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    I mostly have issues with the bearings going bad and that's in effect causing me to strip gears. I'm trying some new bearing I bought off of Ebay here http://www.ebay.com/itm/151644165919 and they were just delivered today. I'll have to test them soon.

  9. #9
    RC Qualifier ausprime's Avatar
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    Quote Originally Posted by jdavi519 View Post
    What happens with the stock diffs, is there is also flex in the plastic when under power. So this moves the gear mesh apart slightly causing a misalignment. This is what breaks them. Shimming helps to kind of preload the gears to keep them in place better.
    On my E-revo brushless edition I was having the same issues, I replaced both the diff cups and housings with all aluminum along with shimming them. I have yet to really beat on them hard, but now there is no more flexing in the housings so in theory they should be stronger.
    Yes very true.
    But even with alloy cups and cases. They still use weak pot metal for the spider gears, and there is only 4 gears (2 spider gears, and 2 sun gears).



    But with the 1/8 scale diffs, there is 4 spider gears, and 2 sun gears. This provides more contact area, making it more durable. And they also use bigger bearings.
    1/8 scale diffs with plastic cups, are stronger then 1/10 scale diffs with alloy cups.
    By the time you buy all the alloy for the 1/10 diffs (cups and cases), you could have brought some 1/8 scale diffs, and still have some change left over.

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  10. #10
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    The 1/8th scale diffs aren't direct drop in right? I'm not experienced enough if I have to mod the crap out of it for it to work

  11. #11
    RC Qualifier ausprime's Avatar
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    Quote Originally Posted by Xboxmember1978 View Post
    The 1/8th scale diffs aren't direct drop in right? I'm not experienced enough if I have to mod the crap out of it for it to work
    No, you will need bigger diff cases like the UE ultralites $135 for front and rear http://www.unlimitedengineering.com/...ore/13551.html

    Or FLM hybrids $140 for front and rear(Comes with everything you need, except for the diffs it self.
    Front http://www.stormerhobbies.com/cgi-bi...cs&pn=FLM17700
    Rear http://www.stormerhobbies.com/cgi-bi...cs&pn=FLM18700

    2X Hyper 7TQ diffs
    http://www.dollarhobbyz.com/ofna/hyp...ferential.html

    If you go with the Ultralites, you will need to get some Revo stub axles (5454) with the threaded part cut off. You will need a dremel, grinder or hacksaw to cut the threads off the revo stub axles. Or your local mechanic, if you don't have anything to cut with.
    Here is a link for the stub axles: http://www3.towerhobbies.com/cgi-bin...?&I=LXHFY7&P=7
    And if you wanted to use the Traxxas steel CVD's for the axles, you will need to use the extended drive cups (5153R) . Especially when using RPM true tracks.
    Here is a link to the Extended drive cups http://www3.towerhobbies.com/cgi-bin...?&I=LXTPP0&P=7
    Some shims for the pinion gear shaft.
    http://www.amain.com/product_info.ph...mm-shim-kit-10 &
    http://www.amain.com/product_info.ph...10x01mm-Shim-8
    Some shims for the diff, to the outer diff case.
    http://www.amain.com/rc-cars/tekno-r...kr1222/p231848 & http://www.amain.com/rc-cars/protek-...h-5904/p188792

    The 1/8 scale diffs, still used 6mm output shafts. But the drive cup and output shaft is one piece. So you need to remove the hyper TQ output shafts from the diff. and replace them with the output shafts you made from the Revo stub axles.

    The center drive cup has an 8mm bore. So the stock 6mm center shafts wont fit on the 8mm pinion shaft. So you would need to use a dog bone type of center shaft, and 2 drive cups with 8mm bores (1 cup for each diff).
    The transmission side is only 6mm. so you can use any drive cups that have a 6mm bore, for both sides of the transmission.

    Total cost is about $200, to not have to worry about them anymore.
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  12. #12
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    If I get the FLM Hybrids my stock gears just install right into the new diff cases?

  13. #13
    RC Qualifier ausprime's Avatar
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    Quote Originally Posted by Xboxmember1978 View Post
    If I get the FLM Hybrids my stock gears just install right into the new diff cases?
    No. There's 2 different cases from FLM.
    One suits the stock traxxas diffs and bearings (FLM10200 and FLM10300).
    The other (that i linked you to) has different dimensions for the larger 1/8 scale bearings. (FLM17700 and FLM18700)
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  14. #14
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    [QUOTE=ausprime;6123025]Yes very true.
    But even with alloy cups and cases. They still use weak pot metal for the spider gears, and there is only 4 gears (2 spider gears, and 2 sun gears).



    But with the 1/8 scale diffs, there is 4 spider gears, and 2 sun gears. This provides more contact area, making it more durable. And they also use bigger bearings.
    1/8 scale diffs with plastic cups, are stronger then 1/10 scale diffs with alloy cups.
    By the time you buy all the alloy for the 1/10 diffs (cups and cases), you could have brought some 1/8 scale diffs, and still have some change left over.


    Just a quick diff question
    When you tighten the ring gear to the spider assembly, how tight do you tighten those 4 screws?
    I recently rebuilt my diff and I tightened those screws quite a bit and then the assembly would not move .I had to back those screws out quite a bit to free up the ring gear . I used mobil 1 synthetic grease . I had it handy so I used it .
    Can you guys give me some guidance on those 4 screws ?
    Thank you

  15. #15
    RC Champion zoraduntov's Avatar
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    .....cant get the pic to work

  16. #16
    RC Champion zoraduntov's Avatar
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    ....................

  17. #17
    RC Qualifier ausprime's Avatar
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    I think your talking about the spider gears binding up when you tighten down the ring gear?
    If your diff uses a flat gasket, you could use a thicker gasket.
    But if its the orange o-ring type. you could get some thinner shims for the cross pins that the spider gears use.
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  18. #18
    RC Champion zoraduntov's Avatar
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    I used all TRx products..The rubber black gasket .

    Its in now but the next time should I use a thicker gasket ?

    Should those screws be tight ?

  19. #19
    RC Qualifier ausprime's Avatar
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    You want it tight enough that oil don't leak out.
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  20. #20
    RC Champion zoraduntov's Avatar
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    should it spin free?

    Anyway...

    You have a nice looking rig there !
    Last edited by zoraduntov; 12-09-2015 at 03:42 AM.

  21. #21
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    you can do all sort of things to your diffs. there are plenty of "upgrades". however i would surely start with some shimming on the stocks first (cheapest option). imho it is important to buy new diffhousings too if you rebuild your diffs. are there some other "tuning" you have done to your drivetrain? e.g. steel shafts?
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  22. #22
    RC Champion zoraduntov's Avatar
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    No Its all stock except for the Mobil 1 synthetic grease
    running 6s
    Only broke that 1 differential and 2 plastic TRX axles
    Ive had it about 3 years

  23. #23
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    so then you have no problem at all.

    maybe the OP can say something to that issue too.
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  24. #24
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    Quote Originally Posted by ausprime View Post
    No. There's 2 different cases from FLM.
    One suits the stock traxxas diffs and bearings (FLM10200 and FLM10300)
    Have you heard good things about them? I wonder if that would be a good idea to get next

  25. #25
    RC Qualifier ausprime's Avatar
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    Quote Originally Posted by Xboxmember1978 View Post
    Have you heard good things about them? I wonder if that would be a good idea to get next
    I wouldn't buy them again. Only because once you go to 1/8 diffs, you never go back to 1/10.
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  26. #26
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    Was it because they still don't hold up?

  27. #27
    RC Qualifier ausprime's Avatar
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    Yea, all it takes is a bad knock. but it's mainly the bearings that didn't last.
    i didn't have any problems with the ring and pinion. It was ether the bearings, or the spider gears that failed in my 1/10 diffs.
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  28. #28
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    That's mostly my issue now, the bearings not lasting at all, I'm not sure if the aftermarket ones I ordered and posted above will help or not

  29. #29
    RC Qualifier ausprime's Avatar
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    New bearings are always going to help. But the size of the bearing makes a big difference.

    Stock diff bearing sizes:
    diff cup bearing 10x15x4mm,
    Ring gear side 8x16x5mm
    Pinion bearings 6x12x4mm

    1/8 diff bearing size:
    8x16x5mm for all 4 diff bearings.
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  30. #30
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    For the FLM 1/10th diff case that you posted it says under the description "This bulk accepts the newer Maxx gear diffs, Traxxas part# 5379X" So they are only for the E-Maxx brushless?

    EDIT: Nevermind. I see it also works for the T-Maxx 3.3 too
    Last edited by Xboxmember1978; 12-09-2015 at 09:20 PM.

  31. #31
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    Quote Originally Posted by ausprime View Post
    No, you will need bigger diff cases like the UE ultralites $135 for front and rear http://www.unlimitedengineering.com/...ore/13551.html

    Or FLM hybrids $140 for front and rear(Comes with everything you need, except for the diffs it self.
    Front http://www.stormerhobbies.com/cgi-bi...cs&pn=FLM17700
    Rear http://www.stormerhobbies.com/cgi-bi...cs&pn=FLM18700

    2X Hyper 7TQ diffs
    http://www.dollarhobbyz.com/ofna/hyp...ferential.html

    If you go with the Ultralites, you will need to get some Revo stub axles (5454) with the threaded part cut off. You will need a dremel, grinder or hacksaw to cut the threads off the revo stub axles. Or your local mechanic, if you don't have anything to cut with.
    Here is a link for the stub axles: http://www3.towerhobbies.com/cgi-bin...?&I=LXHFY7&P=7
    And if you wanted to use the Traxxas steel CVD's for the axles, you will need to use the extended drive cups (5153R) . Especially when using RPM true tracks.
    Here is a link to the Extended drive cups http://www3.towerhobbies.com/cgi-bin...?&I=LXTPP0&P=7
    Some shims for the pinion gear shaft.
    http://www.amain.com/product_info.ph...mm-shim-kit-10 &
    http://www.amain.com/product_info.ph...10x01mm-Shim-8
    Some shims for the diff, to the outer diff case.
    http://www.amain.com/rc-cars/tekno-r...kr1222/p231848 & http://www.amain.com/rc-cars/protek-...h-5904/p188792

    The 1/8 scale diffs, still used 6mm output shafts. But the drive cup and output shaft is one piece. So you need to remove the hyper TQ output shafts from the diff. and replace them with the output shafts you made from the Revo stub axles.

    The center drive cup has an 8mm bore. So the stock 6mm center shafts wont fit on the 8mm pinion shaft. So you would need to use a dog bone type of center shaft, and 2 drive cups with 8mm bores (1 cup for each diff).
    The transmission side is only 6mm. so you can use any drive cups that have a 6mm bore, for both sides of the transmission.

    Total cost is about $200, to not have to worry about them anymore.
    First, thanks for all the great info. Just signed up here and I've been learning alot.

    If I order the hyper 7tq diffs I notice it has the side cups that I replace with the extended ones since I'm going to be running all traxxas cvd's right? But what cup do I use for the center drive shaft connection? Notice in the photo it doesn't come with one?

    Also do I need to get the revo stub axles and modify them to work if I'm going the FLM hybrid way? Or is that only if I was using the UE diff cases? Thanks for any info
    Last edited by LoneWolf8o; 12-10-2015 at 08:06 AM.

  32. #32
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    yep, still need to use cut revo stubs, personally ild just fit some lst diffs...

  33. #33
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    Quote Originally Posted by wilsonj1018 View Post
    yep, still need to use cut revo stubs, personally ild just fit some lst diffs...
    Why do u feel that's better?

  34. #34
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    Im currenly running the lst diffs. I have an flm rpm emaxx running lots of powet, I originally had the flm hybrids eith hyper 7 diffs, and still blee those bearings. I recently took the time to rebuild thosr and sell them to perform the lst mod, ever since I love this truck more as I haven't had any issues, the lst diffs look beastly!! And well built. So I assume my diff issues will not be a problem any more. The mod for the lst diffs actually isn't all that bad, time and patience! !! Lots of threads on how to do it, I myself have one on the process.

  35. #35
    RC Qualifier ausprime's Avatar
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    Quote Originally Posted by LoneWolf8o View Post
    First, thanks for all the great info. Just signed up here and I've been learning alot.

    If I order the hyper 7tq diffs I notice it has the side cups that I replace with the extended ones since I'm going to be running all traxxas cvd's right? But what cup do I use for the center drive shaft connection? Notice in the photo it doesn't come with one?

    Also do I need to get the revo stub axles and modify them to work if I'm going the FLM hybrid way? Or is that only if I was using the UE diff cases? Thanks for any info
    The center drive cups, use a 8mm bore. so any 1/8 drive cups with an 8mm ID will work.
    Here is an example http://www.unlimitedengineering.com/...ore/85038.html

    If you buy the FLM hybrids, new in pack. You wont need to buy the revo stub axles.
    FLM will supply you with output stubs in the hybrid kit.

    You can see the FLM output stubs in the picture below
    Last edited by ausprime; 12-10-2015 at 05:23 PM.
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  36. #36
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    Thanks for the info

  37. #37
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    When I did this:
    Notice there is an O-ring that goes between the pinion drive cup, and outer pinion bearing. This will stop the pinion from sliding in and out. The 8mm and 10mm shims, will stop the diff from moving around inside the diff cases.
    The pinion gear was riding to far up on ring gear. It was causing a rough clicky binding type motion. Should I rely on Or will the center driveshaft, once connected, hold the pinion gear back against the bearings? I apologize, I didn't realize this thread was for emaxx.
    Last edited by Briber; 01-04-2016 at 01:19 PM.
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  38. #38
    RC Qualifier ausprime's Avatar
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    Quote Originally Posted by Briber View Post
    When I did this:
    Notice there is an O-ring that goes between the pinion drive cup, and outer pinion bearing. This will stop the pinion from sliding in and out. The 8mm and 10mm shims, will stop the diff from moving around inside the diff cases.
    The pinion gear was riding to far up on ring gear. It was causing a rough clicky binding type motion. Should I rely on Or will the center driveshaft, once connected, hold the pinion gear back against the bearings? I apologize, I didn't realize this thread was for emaxx.
    Yes! I would screw the drive cup onto the pinion, while the diff case is opened. This way you can push the pinion up against the the inner pinion bearing while attaching the drive cup.
    Then you can screw the 2 diff cases together.
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