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  1. #1
    RC Qualifier
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    diff fluids and rebuild

    I just changed rebuilt all my diffs, 100k center, 20k front, 10k rear. Will know Tuesday how these are working for med->high grip indoor clay track. I can't imagine going thinner on the front/rear, these already have a lot of diff action.

    Couple other tips for rebuilding your diffs --

    For access, just remove the bumper (4-5 bolts), remove the hinge brace bolt, and then two bolts will split the diff housing in half. Some of the videos I watched on YouTube made it seem like you had to tear apart the whole thing, shock tower and all, for access. No need, the car was designed so that you can leave the front/rear assemblies on while you split the diff housing in half.

    Use a new plastic housing (might as well, they come in the rebuild kit), and pre-thread them with your screws before you tighten down the gear, so that you are applying minimal torque during assembly. The rubber gasket is super thin and easily torn during this stage of the rebuild. Also hold the whole thing by the housing and not the gear when tightening -- you don't want to be twisting the gear against the gasket.

    Also a good time to check your bearings.
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  2. #2
    RC Turnbuckle Jr. Jimdog's Avatar
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    Good time for this thread. All the new guys will be wondering how to do this.
    WOW! Look at those pieces fly!

  3. #3
    RC Competitor
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    High bite indoor clay : Guys down there are running 7 k rear , 7 k cent & 3 k front with excellent results in the SCT tekno,losi etc.

    Hmmm...

  4. #4
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    Yeah, pretty much all modern 4wd cars use diff fluids in that range, I suspect it matters a lot how fine the teeth are, the spacing between the spider gears, etc. Really just got to try things yourself, I'll see how my car responds, the previous fluids were totally out of whack, but in general you want thicker in the front IMO.

    What probably makes the most sense is to check out a well setup Tekno and feel the diff action on that to get a good feel for the ballpark. I know roughly what works in my other cars, and 10k in the rear feels close.

    The other factor is that thinner fluid tends to leak more, so that's another compromise between performance and maintenance.

    This is a pretty good video on diff fluid tuning:

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  5. #5
    RC Qualifier Fordbronco1995's Avatar
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    Hows the factory diff weight perform? Decent?
    Slash 4X4 bunch of upgrades handful of shiny parts

  6. #6
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    Quote Originally Posted by Fordbronco1995 View Post
    Hows the factory diff weight perform? Decent?
    I don't know, it's been so long since I had factory built diffs in my car I couldn't tell you.
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  7. #7
    RC Turnbuckle Jr. El Sob's Avatar
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    Factory is 30,000 in the front differential and grease in the rear. I am a basher and keep the front differential stock. The rear gets 100,000. That way I get better straight line traction. Like Posi-Traction in a Chevrolet.
    Member of the 10,000 + posts club! Here to help!

  8. #8
    RC Qualifier
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    I'm going to the track TODAY. Will let you know how the diffs are working.


    Edited for language abuse. If you see a starred out word in your post, you must edit it out to avoid earning warning points.
    Last edited by cooleocool; 01-12-2016 at 12:47 PM.
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  9. #9
    RC Qualifier thesmogman's Avatar
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    I just swapped in my racing diff's to break them in and I was pleased at how the truck worked
    Front 10k 2k rear with the slipper and I changed to the plastic hub's in the rear. Wow, it was better but this is on street with bald tires.

    Gotta make the trek to the track soon. Let us know I still think you need to try lower center diff oil's. I didn't believe it til I tried it!
    Slash 4x4 Tekin Gen II w/Pro4 4000kv

  10. #10
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    I think my center diff is leaking a bit, might try 50k next time I rebuild. But sometimes the track has a really tough rhythm section where you need full 4WD acceleration, so having a thick center diff is beneficial, maybe at the expense of handling. I wrote a long blog post on this.

    http://razorrc.tumblr.com/post/13004...ials-explained
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  11. #11
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    Yup, 20k and 10k are pretty good. Still running 100k center, will probably leave it that way until the next rebuild.

    Car is pretty good, going to go to 1.5mm pistons F/R with 30wt oil, not quite enough shock pack. I really need slightly stiffer springs, but they don't make 'em, so...
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