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  1. #1
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    Cool Tmaxx 2.5 differential spool

    I have recently tore up my rear differential gear, and was going to just replace them with the stock parts 4981. But found out there was a solid spool replacement part 4981x. Has anyone installed the differential spool on their tmaxx 2.5? Does it work like a posi-traction? They say not to run it on pavement, what would it do, tear up some other gears if i ran it on pavement? Just wondered what other users are doing for their differential gears on the tmaxx 2.5

    Thanks.

  2. #2
    Banned by Warnings Phroziac's Avatar
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    It won't work anything like positraction. Positraction is a complex style of differential that gives more traction (by powering both wheels), but still allowing for slip in cornering. If you want that, then see if you can find a ball differential for the t-maxx. Or if you can modify one to work in it. That'll be pretty close to posi, but not much like it.

    The spool will give excellent traction. And it'll ruin your handling unless your running in real loose stuff (fresh powder snow, sand, loose dirt....water...) If you run it on pavement you probably will get annoyed and stop before you tear anything up. I've rode in real cars with spools on the street, cornering is NOT fun. The whole car shakes and bounces through the corner, lol. Of course, your t-maxx won't beat you up for it like a real car.

    Interestingly though, i've heard that stock cars run spools. (Spools aren't bad in REALLY big corners..still seems like it wouldn't be fun to me though).

    And if you're just drag racing the truck for some reason, a spool will be excellent.

  3. #3
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    I agree with Phroziac. A spool will really limit what you can do with your maxx by limiting your cornering ability.

  4. #4
    Banned by Warnings Phroziac's Avatar
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    I dunno about that. If you're running on these hard surfaces why didnt you get a 4tec?

  5. #5
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    Thumbs up Differential spool

    Hey thanks guys for your input. I think i'll just stick with the stock gears, and loosen up the slipper clutch. And perhaps quit thrashing on it so hard! But thats what they are for am i right? I have a little track set up in my backyard with some banked corners and an aggresive dirt mound for a jump. Sometimes i hit it a little harder than i should. I run that thing everywhere on gravel, grass, pavement, dirt, you name it. So the all around versatility of the stock differential seems to be the ticket. Or perhaps i'll check into a ball differential. But anyway thanks again for the input.

  6. #6
    RC Turnbuckle Jr. BlueMonster's Avatar
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    I am going to offer a differing opinion.

    I have been running a spool in the rear for a very long time. Once I upgraded the rear axles to CVD's, I have not had a single issue with them. They do make it a little arder to turn a tight corner on a hard surface, but that is the only problem I have come across.

    I say install some CVD;s in the rear and drop in the spool and see how you like it.
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  7. #7
    Banned by Warnings Phroziac's Avatar
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    You just said basically what i said (though i didnt mention breakability). And CVDs arent that great, try bluestar swing shafts No cross pins to come out. CVDs are a pretty horrible design. (I have LOTS of experience with this).

  8. #8
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    I have the spool in the rear with CVD's and it works just fine. I found that it really helped the Tmaxx grip and go. Also if you plan on climbing any hills you will like it. I just installed the megatech 1.6hp Q series and my god does the truck haul ***. No problems yet with the spool and CVD's. I dont race I just use the truck at the BMX track to jump and and have fun with.

  9. #9
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    Sounds like I should get a spool. How bad are they in pavement? I do most of my running on loose dirt, gravel, grass, and on pavement when I tune it.
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  10. #10
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    I run on pavement and have not had any problems so far that I noticed I dont know what others are having for problems on pavement. I say just get it its cheap and you'll love it.

  11. #11
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    The spool is fun to play with but not all the time. I've got one in a diff so if I want to throw it in I can. Slow speed steering sucks, but high speed steering whips right around. Or like if you take a somewhat high speed turn it the grass it will just standup on the outside rear tire and you may control it on one tire for a while, but it would usually flip over on me.
    They are fun, but they get old after awhile of going after your upside down Maxx.

  12. #12
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    If your going to race it, run a spool if you just want it to bash around here and there, pack the diff with some of the heaviest nastiest greese you can find.

    I had a 80' malibu that I welded the spidergears in the diff to lock them like a posi/spool would. It was alot of fun going straight but turning corners got annoying, also snapped an axel. Theres somthing to be said about 420HP and 373 gears and trying to rip around a corner with street leagal drag tires.
    Its a T-Maxx thing, you wouldn't understand.

  13. #13
    Banned by Warnings Phroziac's Avatar
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    Sigh, positraction is not a spool. And, everyone knows you should run aftermarket axles with spools/locked diffs!

  14. #14
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    yes I was runnig aftermarket axels when it snapped. i was running strange axels in a ford 9", as for your "Sigh, positraction is not a spool." you have been taught wrong. positraction is when both wheels spin in the same direction and is created when both axels have been locked wether it is with a spool or a clutched posi differential or even welding the spider gears. now what you are calling a "true posi" is called a limited slip wich in turn lets 1 wheel rotate in the other direction of the other. I have probly been drag racing alot longer than you have been driving.
    Its a T-Maxx thing, you wouldn't understand.

  15. #15
    Banned by Warnings Phroziac's Avatar
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    Doh. You're the one thats been tought wrong. If it's locked it's locked, if its a spool its a spool. But positraction is a trademarked name of a differential made by GM...

    http://www.mattsauto.com/d1.htm

    Posi is not the same as limited slip, buy it's a type of limited slip.
    What you're calling posi sounds like an open diff to me. Which is just a plain diff like the ones traxxas makes. (No resistance at all to slippage)
    Last edited by Phroziac; 05-26-2004 at 12:19 PM.

  16. #16
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    Postitraction is Not a Spool

    Positraction is a trade name/ nickname for a limited slip differential that was used in GM vehicles and others. People interchange the word positraction with lockers, spools, and limited slips - which are all completely different things.

    Positraction Definition: "GM's designation for their various Limited Slip Differentials. Became almost generic and was applied to different technologies. Not very active in current models".

  17. #17
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    Hi guys. I think Iv found a thread with some brains.
    Iv built a sh28 big block LWB t maxx from a classic I have.. 3.3 gearbox, gpm carriers, hot racing axles, revo 3.3 front drive shaft shortened, rear dog bones. He's OMG
    I need differential help
    the 1 cogs teeth are wore away & a spider's tooth snapped. I was thinking a spool.
    People are telling me Losi conversion
    YEAH THEY AIN'T GOTTA PAY FOR IT
    What can I do?
    Would a spool work wen I use on roads I do like sliding & drifting

    This is what rounded all the diff teeth. It threw a front Grub so was RWD
    https://youtu.be/VbS1qlWz6a0
    Last edited by Munkley; 10-17-2019 at 04:46 PM.

  18. #18
    RC Champion olds97_lss's Avatar
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    Are you running revo spec diffs?

    I have a BB revo 3.3 and it holds up fine to an LRP28S3. It does have the slayer primary output gears in it, but I have a smaller bell/larger spur on it which compensates for the taller gear somewhat.

    That's with stock nitro diffs and slider axles. My main issue originally were the 2 speed and main input gears. I replaced those with RRP and moved the transmission ahead so I could run 1/8th scale clutch/bell on it. I have a 3 shoe alloy 1/8th set of shoes in it.

    Kind of funny, I finally blew my first revo diff this summer in 10 years of having revo's. The x-pin inside the cup chewed through the side rails and just made a mess out of the rear diff. That was on my 21TM revo. I don't drive the BB one much anymore, just keep it around for the cost/effort I put into it.

    FWIW, a spool will likely move your issue elsewhere and ultimately still be hard on the ring/pinion because there's nowhere for the power to slip to. They say not to run on pavement due to the action of the diff when turning. When you turn a corner, the inside tire slows down and the outside speeds up. With a locked diff, it will either be shoving the inside tire or dragging the outside one, which puts a lot of twisting force on your wheel axles/sliders.
    Last edited by olds97_lss; 10-17-2019 at 05:56 PM.
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  19. #19
    RC Turnbuckle Jr. Nitronaught's Avatar
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    Quote Originally Posted by Munkley View Post
    Hi guys. I think Iv found a thread with some brains.
    Iv built a sh28 big block LWB t maxx from a classic I have.. 3.3 gearbox, gpm carriers, hot racing axles, revo 3.3 front drive shaft shortened, rear dog bones. He's OMG
    I need differential help
    the 1 cogs teeth are wore away & a spider's tooth snapped. I was thinking a spool.
    People are telling me Losi conversion
    YEAH THEY AIN'T GOTTA PAY FOR IT
    What can I do?
    Would a spool work wen I use on roads I do like sliding & drifting

    This is what rounded all the diff teeth. It threw a front Grub so was RWD
    https://youtu.be/VbS1qlWz6a0
    Usually the reason why you have wear on those teeth is due to either the diffs have some play/slop between the pinion and ring gear (fixed by shimming the diffs) or you have the older styl diff cases that have only 2 screws holding them together with a collar. So shim the diffs and when you turn the pinion you should not feel a notchy feeling and the ring gear should not have play in it from side to side.

    This is a good article about it, old, but good. https://forums.traxxas.com/showthrea...ight=shim+diff
    Last edited by Nitronaught; 10-18-2019 at 12:10 PM.
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