Results 1 to 25 of 25
  1. #1
    RC Racer
    Join Date
    Dec 2012
    Posts
    157

    Center diff rebuild

    I'm using 60k silicone oil to refill the diff. I've hit up google and found about half of peeps recommending filling the diff 50%, and the other half suggesting to fill it all the way. Neither had any explanations why. How much do you guys refill? Why?

  2. #2
    RC Champion
    Join Date
    Aug 2012
    Location
    Central NJ
    Posts
    1,245
    I fill all 3 diffs to about 90% to allow for expansion when it heats up. If you fill it all the way to the top where the diff fluid is actually squeezing out excess when you assemble it its pretty much a guaranteed thing that you will blow the seals when it heats up.

    50% fill will not give the action it should have for tuning the diffs Front/Center/Rear and you may as well stick with grease instead.

    What weight are you running in the front and rear. Keep in mind that the power follows the path of least resistance and its a tuning thing to get them balanced. General rule of thumb is the heavier the center diff fluid is more power goes to the front unless you have very heavy fluid in the rear which will kill you in cornering. Mine is set up F/C/R 15/30/5.

  3. #3
    RC Qualifier
    Join Date
    Mar 2012
    Location
    Chehalis, Wa
    Posts
    436
    So would it be a good idea to put some thicker oil in there if I'm looking for all around traction?
    _______^_
    /______l__\____
    l_l O l_____l O l

  4. #4
    RC Champion
    Join Date
    Aug 2012
    Location
    Central NJ
    Posts
    1,245
    Its a balancing act between all 3. If you go too heavy in the center all the power goes to the front and the tires will balloon like crazy up front causing the rear to squat. I actually went down to 30K in the center diff from the stock 50K from too much power to the front.

    If you go too heavy in the front and rear you will end up closer to a locked diff and it will affect cornering.

    Sent from my Transformer Prime TF201 using Tapatalk 2

  5. #5
    RC Racer
    Join Date
    Dec 2012
    Posts
    157
    Quote Originally Posted by JustinThyme View Post
    I fill all 3 diffs to about 90% to allow for expansion when it heats up. If you fill it all the way to the top where the diff fluid is actually squeezing out excess when you assemble it its pretty much a guaranteed thing that you will blow the seals when it heats up.

    50% fill will not give the action it should have for tuning the diffs Front/Center/Rear and you may as well stick with grease instead.

    What weight are you running in the front and rear. Keep in mind that the power follows the path of least resistance and its a tuning thing to get them balanced. General rule of thumb is the heavier the center diff fluid is more power goes to the front unless you have very heavy fluid in the rear which will kill you in cornering. Mine is set up F/C/R 15/30/5.
    That's the first time I've heard 90%, but that makes perfect sense. Thanks! I'll be running 10/60/7 once I take it apart to add some more fluid.

  6. #6
    RC Racer
    Join Date
    Dec 2012
    Posts
    157
    Quote Originally Posted by JustinThyme View Post
    Its a balancing act between all 3. If you go too heavy in the center all the power goes to the front and the tires will balloon like crazy up front causing the rear to squat. I actually went down to 30K in the center diff from the stock 50K from too much power to the front.

    If you go too heavy in the front and rear you will end up closer to a locked diff and it will affect cornering.

    Sent from my Transformer Prime TF201 using Tapatalk 2
    Correct, but I believe stock for the center diff is 100K. Going with a thinner fluid (ie 60K) will give you more traction/ transfer when cornering. Thicker fluid is more like running the slipper. Correct me if I'm wrong.

  7. #7
    RC Qualifier
    Join Date
    Mar 2012
    Location
    Chehalis, Wa
    Posts
    436
    What would happen if I put automotive marine ball joint grease in the center diff.
    _______^_
    /______l__\____
    l_l O l_____l O l

  8. #8
    RC Racer
    Join Date
    Dec 2012
    Location
    Torrance CA
    Posts
    177
    Let us all know...

  9. #9
    RC Racer
    Join Date
    Dec 2012
    Posts
    157
    Quote Originally Posted by Keila72 View Post
    What would happen if I put automotive marine ball joint grease in the center diff.
    No idea. And the problem is if you decided to tune it from there you wouldn't know what the weight was, and if you should go thinner or thicker with the fluid. My 60k was $5 at LHS, probably could be found cheaper online.

  10. #10
    RC Racer
    Join Date
    Dec 2012
    Location
    Torrance CA
    Posts
    177
    Do you think the center diff is that much better than the REVO slipper?

  11. #11
    RC Qualifier
    Join Date
    Mar 2012
    Location
    Chehalis, Wa
    Posts
    436
    I run marine grease in all my bearing on all of my rc cars and in my summits diffs. They say its about 500k weight.
    _______^_
    /______l__\____
    l_l O l_____l O l

  12. #12
    RC Champion
    Join Date
    Aug 2012
    Location
    Central NJ
    Posts
    1,245
    Quote Originally Posted by rvrslt1 View Post
    Do you think the center diff is that much better than the REVO slipper?
    Center diff and slipper are two completely different critters.
    Put both on a track the the center diff will win every time. Its not so much about traction as it is control. With a slipper the power is distributed equally to front and rear. With a center diff your choice of fluids dictates power distribution. With a slipper you have to slow way down going into corners and go easy on the throttle coming out or the rear end will try to pass the front end. With a center diff and fluids tuned correctly you just slow down a bit going into turns then you can come out of the turns under full power as when the back end comes loose it transfers power to the front and pulls it straight. I enter the turns still under power, just backed off, then nail it abour halfway through. Do that with a slipper and you are guaranteed to over steer and spinout. Thicker fluid in the center diff transfers more power to the front. I backed off to 30K and it works for me as I had too much power going to the front under acceleration in the straightaways causing the front tires to balloon like crazy and the rear to squat with no traction. The 30k gives me better distribution under heavy acceleration and resulted in a faster time down the straightaways. Like I said its a balancing act where you get good acceleration on the straightaways and still maintain the advantge over the slipper in the corners.

    10/60/7 may be suitable for your driving style, IDK but I think you will find too much power to the front under heavy acceleration. Its a trial and error thing. All you can do is what you have done and ask others what they run, apply the principle, then tune it to work for you.

  13. #13
    RC Qualifier
    Join Date
    Mar 2012
    Location
    Chehalis, Wa
    Posts
    436
    So a center diff is made for racing. What would you recommend for bashing and trails?
    What fluid is everyone running?
    _______^_
    /______l__\____
    l_l O l_____l O l

  14. #14
    RC Champion
    Join Date
    Aug 2012
    Location
    Central NJ
    Posts
    1,245
    It certainly has the advantage in racing.
    You will hear different views on what to use use the bashing, personally I use the center diff for everything. When bashing and doing high speed runs it gets you out of the hole faster and cuts back the unintentional wheelies when running high power systems.

  15. #15
    RC Qualifier
    Join Date
    Mar 2012
    Location
    Chehalis, Wa
    Posts
    436
    Can you explain exactly how it works. I just bought a slash and the whole transferring power thing is puzzling me.
    _______^_
    /______l__\____
    l_l O l_____l O l

  16. #16
    RC Racer
    Join Date
    Dec 2012
    Posts
    157
    Quote Originally Posted by JustinThyme View Post
    .

    10/60/7 may be suitable for your driving style, IDK but I think you will find too much power to the front under heavy acceleration. Its a trial and error thing. All you can do is what you have done and ask others what they run, apply the principle, then tune it to work for you.
    Yeah, it's a starting point. I'll tune as I go. Thx

  17. #17
    RC Racer
    Join Date
    Dec 2012
    Posts
    157
    Quote Originally Posted by Keila72 View Post
    Can you explain exactly how it works. I just bought a slash and the whole transferring power thing is puzzling me.
    I mostly bash, sometimes hit the track. Most people will suggest the slipper for bashing, but I just don't get it. The control is just so much better with the c diff. I don't care about wheelies. I want to keep the truck pointed the direction I want to go. If you hit up a baseball diamond with the diff, you be amazed by the difference. Only thing is, it won't hold up to 3S.

    Here's an explanation I copied and pasted:

    A centre diff technical explanation:

    In normal operation, power is distributed equally to the front and rear wheels. Plates are alternately attached to the front and rear output shafts inside the viscous coupling. When a rotational difference occurs between the front and back wheels, the plates inside the viscous housing shear inside the contained fluid (a type of silicone) heating it and causing the fluid to thicken. The thickened fluid causes the plates to transfer torque from those that rotate faster (the slipping wheels) to the plates that rotate slower (the wheels with the best traction).

    Basically it would be near impossible to do wheelies with a center differential as when the front tire lift off the ground, the rear tires would be slowed to even out the power distribution.

    Slipper cluth: Like a locked diff. Front and rear wheels will always spin at the same speed. So if you grab the throttle you can maintain a wheelie.

    To sum it up:
    Centre diff will transfer torque between front and back based on traction

    Slipper is 50/50 distribution. Traxxas only rate the centre diff for 2s lipos. A Slipper with revo sized upgrades (plate and heavy duty pads) works well on higher powered setups

  18. #18
    RC Racer
    Join Date
    Dec 2012
    Posts
    157
    Quote Originally Posted by Keila72 View Post
    Can you explain exactly how it works. I just bought a slash and the whole transferring power thing is puzzling me.
    I mostly bash, sometimes hit the track. Most people will suggest the slipper for bashing, but I just don't get it. The control is just so much better with the c diff. I don't care about wheelies. I want to keep the truck pointed the direction I want to go. If you hit up a baseball diamond with the diff, you be amazed by the difference. Only thing is, it won't hold up to 3S.

    Here's an explanation I copied and pasted:

    A centre diff technical explanation:

    In normal operation, power is distributed equally to the front and rear wheels. Plates are alternately attached to the front and rear output shafts inside the viscous coupling. When a rotational difference occurs between the front and back wheels, the plates inside the viscous housing shear inside the contained fluid (a type of silicone) heating it and causing the fluid to thicken. The thickened fluid causes the plates to transfer torque from those that rotate faster (the slipping wheels) to the plates that rotate slower (the wheels with the best traction).

    Basically it would be near impossible to do wheelies with a center differential as when the front tire lift off the ground, the rear tires would be slowed to even out the power distribution.

    Slipper cluth: Like a locked diff. Front and rear wheels will always spin at the same speed. So if you grab the throttle you can maintain a wheelie.

    To sum it up:
    Centre diff will transfer torque between front and back based on traction

    Slipper is 50/50 distribution. Traxxas only rate the centre diff for 2s lipos. A Slipper with revo sized upgrades (plate and heavy duty pads) works well on higher powered setups

  19. #19
    RC Qualifier
    Join Date
    Mar 2012
    Location
    Chehalis, Wa
    Posts
    436
    So if it transfers power from the front to back and back to front would it help if the front and rear diffs were locked?
    _______^_
    /______l__\____
    l_l O l_____l O l

  20. #20
    RC Champion
    Join Date
    Aug 2012
    Location
    Central NJ
    Posts
    1,245
    Again its a balancing act. If you lock the front or rear or both diffs you will lose it in the corners. Differential in itself means the wheels spin at a different rate. Example....when turning left the wheels on the right have to travel a farther distance than the wheels of the left. When under power this scenario will cause the wheels on the left to loose traction and transfer the power to the wheel on the right. Even if you were just going slow the left wheel would drag until the right caught up. Think of it like a marching column, military or a band. Those on the inside of the turn take fewer steps than those on the outside. Anyone ever having served in the armed forces knows that the outside continues to move while the inside to continue the illusion does mark time steps until the outside catches up.

  21. #21
    RC Racer
    Join Date
    Dec 2012
    Posts
    157
    Great explanation! And I might add that the same goes for front to back. If you're accelerating out of a corner it's going to bring more weight to the back. The front will wheelie up a little. That means less traction in the front, and less steering. Running the center diff will help keep the front planted, as well as your left and right tires, so you have more control over your steering.

  22. #22
    RC Qualifier
    Join Date
    Apr 2012
    Location
    Ft. Stewart, GA
    Posts
    594
    Justin do you race or bash? Just wondering before I order more diff fluid.. I'm running 30r 50c 30f... with the 15, 30, 5 setup do you have more high end on the straight away with that setup and more speed in turning? Just trying to get setup before the first GCS here in Savannah..
    Whatever I just said.. I'm probably wrong..

  23. #23
    RC Qualifier
    Join Date
    Mar 2012
    Location
    Chehalis, Wa
    Posts
    436
    Quote Originally Posted by ArmySSG View Post
    Justin do you race or bash? Just wondering before I order more diff fluid.. I'm running 30r 50c 30f... with the 15, 30, 5 setup do you have more high end on the straight away with that setup and more speed in turning? Just trying to get setup before the first GCS here in Savannah..
    Hey. What does all the numbers mean. I think I get it when you say 30r 50c 30f. the diff oil. What's the other number your talking about. 15, 30, 5
    _______^_
    /______l__\____
    l_l O l_____l O l

  24. #24
    RC Champion
    Join Date
    Aug 2012
    Location
    Central NJ
    Posts
    1,245
    Quote Originally Posted by ArmySSG View Post
    Justin do you race or bash? Just wondering before I order more diff fluid.. I'm running 30r 50c 30f... with the 15, 30, 5 setup do you have more high end on the straight away with that setup and more speed in turning? Just trying to get setup before the first GCS here in Savannah..
    I race and bash. With the 15/30/5 it gives me a good balance of cornering and straightaway speeds. I started not far from where you are at 30/50/20 but found my tires were balloning too much and not enough power to the rear on long straightaways. Worked great in corners and on really tight tracks but anything with long straightaways I lost ground that I gained in the corners. Nothing gets on your nerves more than to pass a guy in the corners and hit the long straightaway a good 20 feet ahead just to have him pass you then take him again and repeat over and over. After I changed that guy never passed me again!

    Keila the numbers are diff lube weights Front, Center, Rear.

  25. #25
    RC Racer
    Join Date
    Dec 2012
    Posts
    157
    I think so much of it's personal preference. Slayden set up recommends front: 10-15K, center: 50-100K, rear: 5-7K. This definitely isn't a one size fits all kind of thing. I'm sure ill be experimenting for quite some time.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •