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  1. #1
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    Posi traction straight axle Spool to geared diff Option

    If you want a geared differential instead of a posi traction rear axle
    Tra8577 optional gear set and
    a plastic of aluminum diff cup 8581 or 8581X is available
    Easy install - 30k diff oil > unloads quickly
    100-500k diff lock, limited slip - near posi

    Get out there and play
    fabricator

  2. #2
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    Is it a direct bolt on.....

  3. #3
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    Once assembled with silicone diff oil,
    using the original ring gear
    Yes , replaces the spool
    fabricator

  4. #4
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    Sweet. Thanks for the tip! Just ordered a set.

  5. #5
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    Me too.....can't wait....already took rear end out, and have parts on the table....lol

  6. #6
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    Looks like tra8584 spider gear shafts are needed also
    fabricator

  7. #7
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    Hopefully hobby shop will have them in stock....

  8. #8
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    Yup. #8584 needed too. I assembled everything without diff oil just to check the fit and the gears bound up when I tightened the four 2.5mm ring gear screws. D'oh!! Something is definitely wrong. Below is the parts list I used. Anyone else do this conversion yet? What parts did you use?

    CrasyXMAXX, are you pretty sure that #8577 is the correct gear set?

    #8584 - Spider Gear shaft and bushings (I did not use these bushings)
    #8581X - Aluminum Diff Carrier (I used the bushings that came in this kit instead of the ones that came with #8584)
    #8577 - Gear Set
    #8597 - This is the ring gear that came on the truck
    Last edited by TraxxasTyro; 07-21-2018 at 06:19 PM.

  9. #9
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    Assembled without the plastic washers
    Even with 1 plastic washer installed
    it binds the spider gears a little
    It Works as it should
    fabricator

  10. #10
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    #8597 - This is the ring gear that came on the truck
    CORRECTION: the diff ring gear that came with the truck is #8579

  11. #11
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    Even with 1 plastic washer installed, it binds the spider gears a little
    I just spoke with a Traxxas rep. He confirmed the parts list is correct and that there is binding when both washers are used. He said one customer (myself included) experienced binding with one washer. He said it was OK to leave both metal washers off, just make sure to use both blue rubber seals.
    Last edited by TraxxasTyro; 07-23-2018 at 06:52 PM.

  12. #12
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    open diff build

    Quote Originally Posted by TraxxasTyro View Post
    I just spoke with a Traxxas rep. He confirmed the parts list is correct and that there is binding when both washers are used. He said one customer (myself included) experienced binding with one washer. He said it was OK to leave both metal washers off, just make sure to use both blue rubber seals.
    Just built the diff with no washers.....easy to build....Added 200k diff lube.......that stuff is thick.....can't wait to run it.

  13. #13
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    What keeps the blue seal from being shredded as you drive....

  14. #14
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    silicon diff oil lubricant
    Wonderful Stuff
    fabricator

  15. #15
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    Link to 200k diff oil wanted
    fabricator

  16. #16
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    Ran it finally

    Quote Originally Posted by CrazyXMAXX View Post
    Once assembled with silicone diff oil,
    using the original ring gear
    Yes , replaces the spool
    Ran the truck....it's seems smoother....seemed a little faster......quieter.....until it rolled....and broke the axle housing.....so I've run it 4 times for a total of 40 minutes......first thing to break...not bad

  17. #17
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    Quote Originally Posted by FlyingDutchman View Post
    What keeps the blue seal from being shredded as you drive....
    My question too. I don't know. This whole thing is a bit questionable... having to leave parts off just to get it to work. I have the parts so I'm going to do the conversion, but I don't get a confident feeling about it.

  18. #18
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    Quote Originally Posted by FlyingDutchman View Post
    until it rolled....and broke the axle housing.....
    To what do you attribute the carnage?

  19. #19
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    Not sure....axle housing broke at the screw for the trailing arm on right side.....I took it apart and put one washer on right side in diff....feels better....I put aluminum trailing arms on out of the box...also aluminum links.....could have broke because there's no flex in the rear...

  20. #20
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    Quote Originally Posted by FlyingDutchman View Post
    Not sure....axle housing broke at the screw for the trailing arm on right side.....I took it apart and put one washer on right side in diff....feels better....I put aluminum trailing arms on out of the box...also aluminum links.....could have broke because there's no flex in the rear...
    If you really want to throw money at it, there's an aluminum axle housing out on ebay. $200!

  21. #21
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    Throw money

    Quote Originally Posted by Kfrye View Post
    If you really want to throw money at it, there's an aluminum axle housing out on ebay. $200!
    I hate throwing money at this.....gonna put stock parts back on til it breaks.....then go aluminum....if it breaks again.....it's gone!

  22. #22
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    I thought the idea was bash it, break it, repair it, repeat?

  23. #23
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    bash, break, fix, repeat

    [QUOTE=ben1272;6461756]I thought the idea was bash it, break it, repair it, repeat?
    I spend more time fixing it then playing with it...lol

  24. #24
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    I average one hour repair for every 15 minutes of play... not a good combo lol.
    I'm the reason why we can't have nice things!

  25. #25
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    run.......break.......fix......run.......break

    Quote Originally Posted by Teae View Post
    I average one hour repair for every 15 minutes of play... not a good combo lol.
    Let me put it this way.....I have a brand new 4s lipo that I haven't even charged yet for it......but the joys of rc.....lol

  26. #26
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    I really enjoy working on the truck and all of my trucks for that matter. But Im not breaking control arms and trailing arms, I keep breaking piddley crap that shuts the truck down. Both center driveshafts, over heating, and not to mention shearing off axle pins in back to back runs.
    I'm the reason why we can't have nice things!

  27. #27
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    I wasn't happy with the way the gears kept binding up when I cinched down the ring gear. Even if I left off both washers, it just didn't feel right. I could turn it - sort of - by hand, but I could feel each tooth as it rotated. Just didn't instill confidence. I even went as far as to order a second aluminum carrier and gear set, but got the same result. Sheesh. Talk about throwing money at something!

    Then I decided to use the 4$ plastic carrier (#8581) and that did the trick! I was able to install the washer as shown in the assembly guide and man is it smooth. Don't know exactly what dimensions Traxxas got wrong with that aluminum carrier, but if you want to do this conversion and save some $$, I recommend staying away from #8581X. Guess time will tell how well the plastic carrier holds up.
    Last edited by TraxxasTyro; 07-27-2018 at 08:43 PM.

  28. #28
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    Quote Originally Posted by Teae View Post
    ...Both center driveshafts, over heating, and not to mention shearing off axle pins in back to back runs.
    What is getting hot? Motor? Trans? I noticed the rear drive shaft gets pretty hot on mine. I have a temp gun on order so I can find the source of the heat. Seems unlikely that the drive shaft is heating up because of the motor since the two don't really come in contact. But, then, I'm a newb. What do I know. I was thinking it might be the trans in which case I better tear it open and make sure it's not dry.

  29. #29
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    My motor gets pretty hot on 4s (about 140 if I dont break anything in a 10 minute run) and on 6s I know Im melting the truck. Ive gotten motor temps of 170 and I got a temp of 220 on the rear pumpkin where the driveshafts enters it. No amount of grease keeps it cool. It just gets hot and oozes out of the diff housing. Im really disappointed with the temp issues on the truck
    I'm the reason why we can't have nice things!

  30. #30
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    Installed 1 million wt Lucas silicon diff oil
    in the front and rear
    Way better-

    The geared diff should have been the stock setup
    They know how to make money = upgrade
    GO TRAXXAS
    fabricator

  31. #31
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    I was just getting used to drifting around the corners....

  32. #32
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    plastic diff case

    Quote Originally Posted by TraxxasTyro View Post
    I wasn't happy with the way the gears kept binding up when I cinched down the ring gear. Even if I left off both washers, it just didn't feel right. I could turn it - sort of - by hand, but I could feel each tooth as it rotated. Just didn't instill confidence. I even went as far as to order a second aluminum carrier and gear set, but got the same result. Sheesh. Talk about throwing money at something!

    Then I decided to use the 4$ plastic carrier (#8581) and that did the trick! I was able to install the washer as shown in the assembly guide and man is it smooth. Don't know exactly what dimensions Traxxas got wrong with that aluminum carrier, but if you want to do this conversion and save some $$, I recommend staying away from #8581X. Guess time will tell how well the plastic carrier holds up.
    Have you run it yet....how did the plastic diff case hold up....

  33. #33
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    The plastic diff housing should hold up under normal use,
    one installed on the front hasn’t had any issues.
    The washers are only to be used in the plastic diff cup
    to prevent wear on the plastic housing

    This upgrade is the most needed
    Shock limiters
    Pinion and spur
    Stiffer springs

    Stock condition is a terrible setup to drive
    >loop an barrel roll city - if not centered steering
    Never adjust stronger spring tension,
    without shock travel limiters installed
    fabricator

  34. #34
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    I'm gonna run mine tomorrow while waiting for my wife to get out of her meeting for work.....then this weekend gonna tear the front and rear diff out and double check them.
    CrazyXMAXX.......What did you use for limiter, what's your pinion/spur gear, and what springs are you using?

  35. #35
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    Small black extra shock mounts-
    comes with slash/rustlers etc
    drilled out to 4mm
    34/47
    Green strip spring on front
    Brown strip spring on rear
    On 6s - walk the wheelie over the hump

    Butter smooth rear diff/with no binding
    Run it a bit to break it in
    Last edited by CrazyXMAXX; 07-31-2018 at 03:35 PM.
    fabricator

  36. #36
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    how did the plastic diff case hold up....
    Ran a pack through it without any issues. I figured the center and front diff use the same carrier and I haven't had any issues with those. But the big thing for me is that there's NO BINDING.

  37. #37
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    less heat

    Quote Originally Posted by TraxxasTyro View Post
    Ran a pack through it without any issues. I figured the center and front diff use the same carrier and I haven't had any issues with those. But the big thing for me is that there's NO BINDING.
    Ran my UDR again......haven't messed with shocks and gearing yet.....made shorter limiting straps......rear end was not as warm as before.....open diff is a huge difference.....this could be a problem as to why drive shaft keep breaking....going to play with gearing and shock set up this weekend....truck is finally coming around to bring fun again.

  38. #38
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    rear end was not as warm as before.....
    Good to hear. I just receive my IR thermometer thing so I'll be poking around with it to see what's causing the drive shaft to heat up.

  39. #39
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    I made several WOT speed runs across a large, concrete parking lot and took the following temps. Ambient temperature was about 98F. Stock everything. 4S. the ESC was difficult to get at so I suspect the temp was probably higher than I measured.
    Rear diff = 115F
    Output bearing 5180a (next to where the rear drive shaft connects to the diff) = 112F
    Center Rear drive shaft = 112F
    Motor, rear = 153F
    Batteries = 98F (ambient)
    ESC = 115F

    Taking the time to disassemble, clean and regrease the front, center and rear diffs and planetary gears has lowered the temps. ...and I'm loving the open diff!
    Last edited by TraxxasTyro; 08-03-2018 at 05:49 PM.

  40. #40
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    Have not had any issues with the open diff
    Works great with 1 million diff oil
    Stops most all of traction rolls
    able to ride bicycle - on 2 side wheels
    Steering out of rolling over many times
    So much better than the stock spool
    fabricator

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