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  1. #1
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    Question Front diff - spider gears broken after 10 mins driving since last diff rebuild???

    Hello

    I've been driving my truck E-Revo Brushless TSM for 2 months without differential issues, 6S lipo most of the time. Except from some Summit shafts and Proline Trencher wheels, all parts are stock.

    A couple of days ago I experienced a clicking sound from the front diff, and the wheels locked sometimes. I ordered ring/pinion 5379X and output gear set 5382X, and rebuilt the differential yesterday, replacing every single gear in it (they we all broken). I applied plenty amounts of 30000 grease on the gears and assembled the truck and it seemed to work fine.

    BUT

    Today I went to the beach and did some jumps on the dunes and racing in the sand, and suddenly the truck seemed to have lost power, and I can see that the front wheels have no power and can rotate almost freely.

    I went home and took out the diff again and realized that both the spider gears in the carrier were broken and had lost several teeth. There were no apparent damages to the output and pinion gears and only small scratches on the ring gear.

    WHY are the spider gears breaking after such a short drive? What could I have done wrong when I assembled it? I just followed the guide, applied a lot of 30000 grease. After assembling the carrier/ring gear, I loosened the screws a bit, as it seemed hard to turn the outputs when it was tightened.

    What could be obvious reasons that makes the diff break twice? I had a drive shaft that broke when the ball bearing were stuck, could something similar happen to the diff?

    I did not do any crazy crash landings, just driving around the sand and made some jumps/loops on the dunes, with on-wheel landings in the loose sand.

    Before I spend another 20$ (I live in Denmark...) and a couple of hours on replacement, I need your advice.

    Any help is appreciated, thanks in advance!
    Last edited by esbenvb; 03-23-2016 at 05:02 PM.

  2. #2
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    6s is the reason. The best advice I can give you is do the Losi diff mod. Thou breaking the spider gears is special. Usually its the ring gear/pinion bearings that break.
    Slash 4x4 / Erbe / Custum Erbe / Bandit VXL

  3. #3
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    i'd guess it's bad luck. did the same thing daily last summer at the baltic sea for 2 weeks and nothing broke. was also running 6s. lst mod is also sth. i'd like to do but I'd take the chance by buying another replacement set or one or two complete diffs from a chop shop. I still have two lying around unused because of the same fear i had: 6s breaking diffs. so far no issues though.

  4. #4
    RC Turnbuckle Jr. Jezza's Avatar
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    6s and the huge trenchers are a culprit.
    Lst 2 diff mod is definetely your best option if you sre running 6s most of the time.
    I had great luck with my stock set up for a yearvwithout issues, simmed them from day one when I got my roller, rarely ran 6s and never had an issue. Now that the lst2 diffs are in, I dont think I will have any issues anytime soon.
    Live life to the fullest

  5. #5
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    trenchers... forgot about them. i had them on and broke some axles. so they really might be the issue. switched to thunder tiger mt4 tires because of that. jezza is right with his statement. maybe lst diffs are needed then.

  6. #6
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    Quote Originally Posted by esbenvb View Post
    Hello
    I ordered ring/pinion 5379X and output gear set 5382X, and rebuilt the differential yesterday, replacing every single gear in it (they we all broken).


    After assembling the carrier/ring gear, I loosened the screws a bit, as it seemed hard to turn the outputs when it was tightened.
    if you rebuild your diffs i would recommend you replace all parts. also the diff carrier, bearings etc. they are usually worn out and if you only replace the gears the probability of your next "failure" increases significantly. mixing up old worn out parts with new ones may cause more trouble than good.

    if the diff does not run smoothly after rebuilding, start again from the beginning. just loosing the screws a little will amost for sure end up with broken gears as you have experienced.

    rebuilding diffs is a very sensitive task. the diff should run freely and smooth but maybe just a tiny little bit tight.

    shim the diffs only if necessary.

    aside of that. with 6s make sure you slipper is set up correctly and you may think of smaller lighter tires (e.g. badlands or the like) for driving. you can still put on your cool trenchers for nice pictures.

    bye
    rhylsadar
    Last edited by rhylsadar; 03-24-2016 at 09:40 AM.
    Exercitatio artem paravit

  7. #7
    RC Racer
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    You mentioned you drive in the sand. I wonder how much maintenance you do after every run. What I found on my brushless Summit is that the sand, rock grains, and dirt will be trapped in the driveshaft cup and around the CVD joint, causing the drive shaft to seize up and very difficult to rotate, which will exert extra resistance for the diff to overcome. In addition, trenchers seems to have good traction (the more traction you have, the more resistance it will put on the driveline).

    What I normally do is that after every run I use WD40 with air spray to lubricate the joints and wash out the dirt and sand. You'll want as little resistance as possible in the driveshaft.

  8. #8
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    What driving situation puts the most stress on the spider gears?

    One wheel landings?
    Donuts with the inside tire in the air ballooning?

  9. #9
    RC Turnbuckle Jr. Jezza's Avatar
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    Quote Originally Posted by Multirotor View Post
    What driving situation puts the most stress on the spider gears?

    One wheel landings?
    Donuts with the inside tire in the air ballooning?
    Lots of factor, there are lots of moving parts involved in these trucks , sometimes the worst damage happens on the least expected experience where you thought that ''shouldn't happen'' , a combination of many many things can go wrong or non.....

    Definetely one wheel landings are dreaded when you cringe out thats going to hurt.
    Stress on the drive shafts, long grass, soft terrains etc could add to all the factors, to tight of a gear mesh etc...you name it

    A nail sticking out of the ground could wipe out your lower arms or even bulkheads...

    Sand stuck in the diffs or bulkheads, siezed bearings etc...all those , you have to be ready when the unexpected happens ...then again like mine for a whole year nothing at all, so I upgraded the trucks even though nothing broke as stock....now I hope it so so called bulletproof..
    Last edited by Jezza; 03-24-2016 at 02:48 PM.
    Live life to the fullest

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