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  1. #1
    RC Qualifier Calebs0615's Avatar
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    Rustler 4x4 to VXL Diff Swap Question

    I'm going to be changing the differentials in my rustler 4x4 to the ones that come from a rustler 4x4 vxl model. I think the parts i need are these numbers: 6879 6882

    I want to be sure before i buy anything. If i buy two 6879 and 6882 each, ill have what i need to change both front and rear right?

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  2. #2
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    Quote Originally Posted by Calebs0615 View Post
    I'm going to be changing the differentials in my rustler 4x4 to the ones that come from a rustler 4x4 vxl model. I think the parts i need are these numbers: 6879 6882

    I want to be sure before i buy anything. If i buy two 6879 and 6882 each, ill have what i need to change both front and rear right?

    Sent from my LGL722DL using Tapatalk
    i actually went ahead and applied the "buy once, cry once" philosophy...and got the 6879R, and 5379x rear, and front, respectively (helical/spiral cut ring and pinion :xo-1 parts i believe), also, #6882X is the XO-1/revo spec. Spider gears with support bar, #3978 is the carrier, which is where i developed a LOT of slop both front and rear, and, as theres no bearings for the output spider gears, the case wears out after the "x-rings" inside of it, resulting in high speed wheel wobble, inability to track straight, etc. Instantly solved with the above-mentioned parts. Sure, ring & pinion was a little more $$, but for the sole purpose of being able, 4 months from now, say "****, they shoulda put these in this from the factory" meaning all is still functioning well/better and no slop to speak of..totally worth it!
    Highly recommend! Also paired with the new style HD CV axles that came out after Hoss...seems allllmost bulletproofed.

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  3. #3
    RC Qualifier Calebs0615's Avatar
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    Quote Originally Posted by Trx4newb View Post
    i actually went ahead and applied the "buy once, cry once" philosophy...and got the 6879R, and 5379x rear, and front, respectively (helical/spiral cut ring and pinion :xo-1 parts i believe), also, #6882X is the XO-1/revo spec. Spider gears with support bar, #3978 is the carrier, which is where i developed a LOT of slop both front and rear, and, as theres no bearings for the output spider gears, the case wears out after the "x-rings" inside of it, resulting in high speed wheel wobble, inability to track straight, etc. Instantly solved with the above-mentioned parts. Sure, ring & pinion was a little more $$, but for the sole purpose of being able, 4 months from now, say "****, they shoulda put these in this from the factory" meaning all is still functioning well/better and no slop to speak of..totally worth it!
    Highly recommend! Also paired with the new style HD CV axles that came out after Hoss...seems allllmost bulletproofed.

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    Thank you. What your saying is i should save up and buy the 6879R and 5379x parts? Which parts solved the slop? Im sorry, I dont really understand how you worded it.

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  4. #4
    RC Qualifier Calebs0615's Avatar
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    So i need 6879R, and 5379x?

    6879r is spiral and 5379x is straight cut isnt it?

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    I'm fairly certain it's the combo that solved the problem in the rear then I went up front and I bought the wrong spider gear kit, so I ended up only cleaning and removing the existing gears while adding a spiral cut ring and pinion and a new carrier. The carrier is the case which houses the spider gears NOT the aesthetic cover that is part of the chassis. That's your differential housing.

    Anyways, the carrier in the front solved the slop, at least, temporarily. However, the rear is solid as a rock now! If your axles wiggle in a circular motion AT the OUTPUT gears (where the thru-pin holds the axles to the diff) then a carrier rebuild kit should suffice.
    My recommendation, unless you are having specific problems with your differentials, if you're going to crack them open once on the wrestler go ahead and upgrade them while you're in there and then the only reason you theoretically should have to get back inside the housings, is the occasional check and re-lube. But yes, i personally suggest upgrading NOW-ish, that way, you haven't "rebuilt" the diffs 5 times in 8 months, to get rid of slop, etc. The money u spend once, pays for itself thrice to ten-fold.



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  6. #6
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    Quote Originally Posted by Calebs0615 View Post
    So i need 6879R, and 5379x?

    6879r is spiral and 5379x is straight cut isnt it?

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    You are correct.

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  7. #7
    RC Qualifier Calebs0615's Avatar
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    Thank you for the help. Im assuming you did the spiral cut in the rear cause its a bit stronger than the straight cut?

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  8. #8
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    Quote Originally Posted by Calebs0615 View Post
    Thank you for the help. Im assuming you did the spiral cut in the rear cause its a bit stronger than the straight cut?

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    Quite a bit stronger! If u google/'tube "difference in spiral(helical) in the automotive world, gears and straight cut gears, you will see the huge difference in contact area as the gears mesh within each other. I personally think its quite significant, even if you are only talking .0030in difference per tooth in 1/10 scale!

    Also, helical cut gears or spiral cut gears, are significantly quieter due to the difference in the way they mesh versus straight gears. think back if you've ever driven a manual Honda Civic and every time you went in reverse it would make this awful "rrrreeeEEEEEEEREREEEEEEE" sound while moving....those are straight cut gears, your 1st - 5th gears are helical cut...hence why u dont hear that noise in forward-direction throughout the gear range. Also I've only been in the hobby for maybe seven or eight months now, and from what I can gather and through my personal experience, Traxxas is more than happy to make it right if you chat feature them on their website having broken apart on your first second third even fifth run while being gentle obviously. Usually if you have proof of purchase etc they have no problem sending you a brand new replacement of their (more) expensive parts.

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  9. #9
    RC Qualifier Calebs0615's Avatar
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    Im pretty smart when it comes to working on cars. But im really happy you told me that about the manual trans. I didn't know that. I have had a 92 civic that was 5 speed and it would whine in reverse quite loudly. I now own a 09 hhr thats manual aswell and it doesn't do that. I always wondered why. You learn something new everyday. Thank you.

    I am going to take your advice and save for the helical gears in the back. I have a question for you though, what made you stay with straight cut in the front?

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  10. #10
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    It’s a crazy difference how much better it meshes. One demonstration to do is put a car on a stand, and rotate either both rear or both front hubs in the same direction which will rotate the center drive shaft and in turn the other two driveshafts. The stock straight cut gears can be smooth but the spiral cut gears? It feels like it has momentum of its own from the extra contract surface and angles. Pricey yes, but boy do they work.
    Last edited by TwoBelugas; 11-11-2020 at 05:11 PM.

  11. #11
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    Quote Originally Posted by Calebs0615 View Post
    Im pretty smart when it comes to working on cars. But im really happy you told me that about the manual trans. I didn't know that. I have had a 92 civic that was 5 speed and it would whine in reverse quite loudly. I now own a 09 hhr thats manual aswell and it doesn't do that. I always wondered why. You learn something new everyday. Thank you.

    I am going to take your advice and save for the helical gears in the back. I have a question for you though, what made you stay with straight cut in the front?

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    I didnt. I also replaced the front with spiral cut R&P, but i had purchased the "regular" spider gear set by accident #6883 is a CENTER DIFF rebuild kit. So im just holding onto it for down the road.

    my front diff had developed major slop just shortly after I replaced / rebuilt the rear diff. But, now, when it's time to do it again hopefully I'll have the XO-1, gearset (spiders) handy and it'll be a clean/lube/pop in new spider gears w/brace.

    Looking forward to testing the longetivity versus stock gears.

    Happy to be of assistance, and i think you've made the right choice on saving for the REAL UP-grade. Ive personally learned the "buy once, cry once" thung the REAL-HARD way and now im realizing i might be ****-near-ballin' if id have done it right the first time till now.

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  12. #12
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    Finally pulling the trigger on the spiral diffs today. Ill try to remember adding pictures.

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  13. #13
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    Quote Originally Posted by Calebs0615 View Post
    Finally pulling the trigger on the spiral diffs today. Ill try to remember adding pictures.

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    Dont forget the spider gear set WITH "I-bar" support!

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  14. #14
    RC Qualifier Calebs0615's Avatar
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    Tra6882x right? I dont need to buy 2 sets do i?

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  15. #15
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    Quote Originally Posted by Calebs0615 View Post
    Tra6882x right? I dont need to buy 2 sets do i?

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    One 6882 x, per axle. So two sets, BUT, u might look out once you open the diff housings and find out that the gears are in good shape what I realized is that once that slop develops, the screws that hold the ring gear onto the diff case come loose and it starts walking....causing the inner spider gears to wear each other out if you pull them out and they're not razor sharp on the teeth edges, and they look to have plenty of " life" (not worn down to nubs) u may not need to put them but don't hate on me when a week after you put it back together and you've played with the truck three times they decide to go lol

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    Quote Originally Posted by Trx4newb View Post
    One 6882 x, per axle. So two sets, BUT, u might look out once you open the diff housings and find out that the gears are in good shape what I realized is that once that slop develops, the screws that hold the ring gear onto the diff case come loose and it starts walking....causing the inner spider gears to wear each other out if you pull them out and they're not razor sharp on the teeth edges, and they look to have plenty of " life" (not worn down to nubs) u may not need to put them but don't hate on me when a week after you put it back together and you've played with the truck three times they decide to go lol

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    That kit is a must in both my gifts as I'm now running 4s and a 2200 KV system with slipper eliminator

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  17. #17
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    So what you mean is the stock ones probably look okay but they wont last but a few runs. I only have the base model 4x4 so they might not even be the same tooth count.

    Okay so im getting two of the gear sets and then a front diff and rear diff? Then ill be all set right?

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  18. #18
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    Quote Originally Posted by Calebs0615 View Post
    So what you mean is the stock ones probably look okay but they wont last but a few runs. I only have the base model 4x4 so they might not even be the same tooth count.

    Okay so im getting two of the gear sets and then a front diff and rear diff? Then ill be all set right?

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    2x. 6882x
    1x 6879R (rear spiral cut gears)
    1x 5379R (front". ")
    And i recommend not going too too high with the diff fluid viscosity, I tried 2 million weight and the truck just ended up barrel rolling every time there was the slightest steering input... So I then switched my front to I believe 500k possibly 100k not sure, and it drove like brand new handles very well.

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  19. #19
    RC Qualifier Calebs0615's Avatar
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    Perfect thank you. I have some 100k that ill put in both. The parts are coming Friday.

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  20. #20
    RC Qualifier Calebs0615's Avatar
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    I appreciate your help. I know the 2ws slash inside amd out but my 4x4 rustler is pretty new territory. Im excited to learn amd tear into this thing.

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