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  1. #1
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    Optional center differential power question

    Last night I was working a little on my slash 4x4 street conversion and I read on the center diff I ordered from Traxxas that it recommended 2s LiPo only cause any higher rated battery could cause damage.
    Iím using Castle Creations Monster X 1/8 Brushless Combo w/1515 Sensored Motor combo. I was planning on running 3-4s batteries, will that center diff be ok?
    Thanks for any input.

  2. #2
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    Yes, the center diff will be fine. When I had a slash 4x4 I usually ran it on 2 and 3s lipo with a 3000kv motor, but I did throw in my mm2 and cc2200kv motor on 3-5s and it handled it just fine. I did swap to the rrp 53t steel center diff spur since a steel spur makes it easier for my to set the gear mesh on a slash since itís more uniform than the molded plastic ones, and the steel spur also is stronger. So I recommend that spur and center diff and around 150k or so center diff fluid for bashing.


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  3. #3
    RC Champion Panther6834's Avatar
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    Quote Originally Posted by Arcor View Post
    Last night I was working a little on my slash 4x4 street conversion and I read on the center diff I ordered from Traxxas that it recommended 2s LiPo only cause any higher rated battery could cause damage.
    Iím using Castle Creations Monster X 1/8 Brushless Combo w/1515 Sensored Motor combo. I was planning on running 3-4s batteries, will that center diff be ok?
    Thanks for any input.
    Possibly...but, not necessarily. It would help if you started the kV of the motor you'll be using. Without knowing the kV, I would venture to say that the center did would be ok on 3S...but, on 4S, possibly not ok. Again, it depends on the kV of the motor.

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  4. #4
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    I remember reading about people saying the plastic center diff is iffy with 3s. I never ran it so I wouldn’t know, but their new diff, the 6780, is much more robust and I run it with my 4s set up with no issues.

    Unless I’m mistaken castle 1515 sold with the MMX as combos are all 2200kv motors, at least the factory ones.

  5. #5
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    Just keep in mind that the 6780 isn't compatible with RPM telemetry just yet, although since it is stock on the HOSS, I am curious what Traxxas is going to do about that.

  6. #6
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    The 1515 is 2200kv for the motor. I just looked at the diff i bought and it is not the 6780 part#.
    Think i could just get the metal housing and metal spur gear for the one i did buy and it would be fine?

    This is one i bought : https://traxxas.com/products/parts/6814

    Didn't know there was an upgraded version or i would have just bought that one.

  7. #7
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    The 6814 is very different from the 6780, I think even the spurs have different number of bolts (3 on 6814 versus 4 on 6780)

    The Hoss versions looks very similar to the 6780 but uses a plastic cup, I believe.

  8. #8
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    Quote Originally Posted by TwoBelugas View Post
    The 6814 is very different from the 6780, I think even the spurs have different number of bolts (3 on 6814 versus 4 on 6780)

    The Hoss versions looks very similar to the 6780 but uses a plastic cup, I believe.
    https://traxxas.com/products/parts/6780 says that it is a replacement part for the Hoss, making it a standard part that it comes with - which is why I am curious how they will do RPM telemetry given that they currently offer a magnet holder for it yet.

  9. #9
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    Quote Originally Posted by Arcor View Post
    The 1515 is 2200kv for the motor. I just looked at the diff i bought and it is not the 6780 part#.
    Think i could just get the metal housing and metal spur gear for the one i did buy and it would be fine?

    This is one i bought : https://traxxas.com/products/parts/6814

    Didn't know there was an upgraded version or i would have just bought that one.
    I would do the flm upgrade if the plastic one cant

    It should be cheaper than the 6780
    I wouldnt want to spend $75 on a center diff

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  10. #10
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    Quote Originally Posted by halygon View Post
    https://traxxas.com/products/parts/6780 says that it is a replacement part for the Hoss, making it a standard part that it comes with - which is why I am curious how they will do RPM telemetry given that they currently offer a magnet holder for it yet.
    https://traxxas.com/explodedviews/Ho...ssion-Assembly

    Looking at the parts list, the hoss comes with 9081 as the diff cup

    https://traxxas.com/search?keyword=9081

    Which is plastic. 6781 is the optional metal upgrade option listed next to 9081.

  11. #11
    RC Turnbuckle Jr. olds97_lss's Avatar
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    There are now 2 center diffs that fit, so it depends which one you buy. I believe the plastic cup/spur version is the one recommended for 2S only. That's the one I got for my stampede when I went 3S. It would warp after about 5 minutes of use and the spur gear would die and oil would fling all over from the diff as the seal warped. I was running a max10sct/3665 3100kv in it when I tried the plastic cup. So not near the power I'm pushing through it now.

    I replaced the cup with a fast lane machine cup, but stuck with the plastic gear. It's been fine since, other than blowing an occasional spur because the pinion moved or the motor moved.

    I now run 3S only on it with a 4074 2200kv 1/8th motor and 150A 1/8th esc with 20/54 gearing, MIP X-Duty's and trencher 2.8's. I'm running 300K in the center diff, but could bump that up to 500K now that I have the slash chassis on it. When it was a stampede, 500K was too much and it just wheelied everywhere, but 300K just calmed it down a lot. Would still wheelie if I got on the throttle hard, but otherwise, it would just take off really quickly.
    https://www.youtube.com/c/olds97lss

  12. #12
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    At the risk of sounding pedantic, there are three

    6814: the 2s recommended older one with plastic cup and spur

    6780: the all metal diff that came out quietly last year

    The Hoss diff: looks like 6780 but with 9081 plastic cup instead of the 6781 metal cup.

  13. #13
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    Quote Originally Posted by TwoBelugas View Post
    At the risk of sounding pedantic, there are three

    6814: the 2s recommended older one with plastic cup and spur

    6780: the all metal diff that came out quietly last year

    The Hoss diff: looks like 6780 but with 9081 plastic cup instead of the 6781 metal cup.
    If the exploded view is correct, then they are introducing yet another configuration of the center diff. — for my point though, the spur gear is still the same with the four bolt pattern, which is why the current magnet holder doesn’t fit.
    Last edited by halygon; 08-27-2020 at 07:57 AM.

  14. #14
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    Well i ended up ordering the metal diff cup and a robinson racing 53T spur gear. That should make it ok then. I hope....

  15. #15
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    Quote Originally Posted by Arcor View Post
    Well i ended up ordering the metal diff cup and a robinson racing 53T spur gear. That should make it ok then. I hope....
    I know you said originally you ordered the plastic diff. Did you keep that one for the gears to go in the cup you ordered?

  16. #16
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    Oh yeah, i'm still slowly working on the build. Still need to dye chassis black and so on.
    Once i read all the stuff here, i started looking for a metal diff cup and a steal spur gear just to be on safe side.
    Should see them come in saturday or monday i think.

  17. #17
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    Quote Originally Posted by Arcor View Post
    Oh yeah, i'm still slowly working on the build. Still need to dye chassis black and so on.
    Once i read all the stuff here, i started looking for a metal diff cup and a steal spur gear just to be on safe side.
    Should see them come in saturday or monday i think.
    Awesome. Good luck then. installing my center diff made my slash come to life. I found 60k weight to work best for me as it gave me the ability to go full throttle without lifting on the front end, but still gave me ability to gun it and do a controlled wheelie. Some folks say to throw in 100k+ diff oil, but I started with 100k and it basically felt like the slipper clutch.

  18. #18
    RC Turnbuckle Jr. olds97_lss's Avatar
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    Quote Originally Posted by halygon View Post
    Awesome. Good luck then. installing my center diff made my slash come to life. I found 60k weight to work best for me as it gave me the ability to go full throttle without lifting on the front end, but still gave me ability to gun it and do a controlled wheelie. Some folks say to throw in 100k+ diff oil, but I started with 100k and it basically felt like the slipper clutch.
    For a slash with slash sized tires, that's probably true. Also depends on which diff you end up with. v1, v2, v3 as the cup is different for each, so fluid likely moves around in it differently for each. So 100k in one may feel like concrete and in another may feel like nothing.

    300k gives me pretty good control with 2.8 MT tires on my stampede on 3S. I have the v1 but aluminum aftermarket cup.
    https://www.youtube.com/c/olds97lss

  19. #19
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    Quote Originally Posted by olds97_lss View Post
    For a slash with slash sized tires, that's probably true. Also depends on which diff you end up with. v1, v2, v3 as the cup is different for each, so fluid likely moves around in it differently for each. So 100k in one may feel like concrete and in another may feel like nothing.

    300k gives me pretty good control with 2.8 MT tires on my stampede on 3S. I have the v1 but aluminum aftermarket cup.
    Good point. I bought the 6780 full gear/cup/gear combo to add to my specific situation.

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