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Spidergears in Rear Diff keep blowing

DangerD

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Hi,

is there any trick to prevent rear spider gears from cracking?

My first stock rear diff did break after around 10 packs (gears and casing, propably noticed it to late). I switched to a tekno steel case and complete new internals and after another 10 packs one of the little spider gears broke again in the rear.
I still run the stock stock plastic front case and a m2c aluminium middle case with the frist gear sets from the original kit with no issues so far. Only the rear keeps breaking on me.
Stock f50k/m100k/r100k oil setup.

Could lower oil in the rear help?
 

Billl DeLong

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Which chassis are you talking about?
What size motor and battery are you running?

Why so thick of fluid in the rear diff?
What traction condition are you running on?

What size wheels are you running?
Are you doing lots of wheelies and hard acceleration?

I think the thickest I have ever ran in the rear was 20K for any car, even on high traction turf!

 

lampshade9909

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Hi,

is there any trick to prevent rear spider gears from cracking?

My first stock rear diff did break after around 10 packs (gears and casing, propably noticed it to late). I switched to a tekno steel case and complete new internals and after another 10 packs one of the little spider gears broke again in the rear.
I still run the stock stock plastic front case and a m2c aluminium middle case with the frist gear sets from the original kit with no issues so far. Only the rear keeps breaking on me.
Stock f50k/m100k/r100k oil setup.

Could lower oil in the rear help?
Are you bashing hard on 6s? There’s a guy local to me who I met recently who was having a similar issue with his MT410. He said he was using 6s and doing insane backflips and it would break on landing when he was hard on the throttle. He admitted to being pretty abusing to it though. He said the upgrade to diff housing (or casing, not sure which) was what solved it for him. I asked him about fluids as well and he wasn’t sure if that was a factor or not. Does this sound like your situation? I don’t have his contact info or I’d ask for you.
 

lampshade9909

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Why so thick of fluid?

What size wheels are you running?

I think the thickest I have ever ran in the rear was 20K for any car, even on high traction turf!
It’s recommended to use thicker fluid with heavier tires or when bashing, correct? Is there a safe max for Tekno on diff fluid for the diffs in general regardless of racing/bashing? Some bashers have diff fluid as high as 500k or even 1-20 million. I’m not sure if their diffs are fundamentally different though.
 

Billl DeLong

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I can't think of any reason why "bashing" should require thicker fluid, all that will do is take away rear traction and make the car more difficult to drive... as far as stripping planetary gears, I question if you are smashing the throttle all the time, if so then it's just a matter of learning throttle control and softening your acceleration to help prevent stripping gears ;)
 

lampshade9909

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as far as stripping planetary gears, I question if you are smashing the throttle all the time, if so then it's just a matter of learning throttle control and softening your acceleration to help prevent stripping gears ;)
ESC settings can help with that too.
 

DangerD

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It is a wide et.48 chassis with mt410 towers etc.
Max8 Combo 2200kv on 62, 15T pinion. Punch on 3 (5 is max).

The diffs are filled as suggested in manual. Both diffs died on offroad/bashing mainly sand, gras, gravel ground.

Both diffs died while using proline big joe II wheels, i also had some runs with badlands 3.8.

I jump alot 2-3m hight, never trottle on landing, however i am not easy on the gas on acceleration etc.

I will switch to a 1650kv motor and stay on 15/16T pinion. However i guess this will only put more torque on the drive train even if my max speed wil go down.

I wonder why only the rear dies and i have no issues with the center diff running the same oil. Looks like the spider gears cant hold up to heavy wheels.
 

Billl DeLong

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I would try to see if you can add some 0.2mm shims behind each of the planetary gears, this should tighten the mesh and be less likely to strip, it will also make the diff action more tight so you'll definitely want to go with lighter diff fluid... consider going with 20K and see how that works... not sure if these are the size shims to get but I plan on rebuilding my truck tomorrow and will take some measurements to confirm these will work, posting link for now just so I don't have to search for the shims again:
https://www.amainhobbies.com/protek-rc-3.6x12x0.2mm-differential-gear-washer-10-ptk-h-5914/p188802
 

lampshade9909

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Take all of your spider gears and put them on the cross pins on both sides, does they all spin freely? Or does it get stuck somewhere? If it gets stuck somewhere, your cross pins are getting bent from something related to those tires... I'm really curious to see what this problem is. Have you tried contacting Tekno support?

Obviously, you could just not use those Big Joe tires, but there has to be a reason to this that we can discover. Those tires aren't even that heavy right? How much does one single Big Joe tire weigh? Less than a pound right? Belted Trenchers weight more than 1 pound per tire... People use those without having this problem.

When you open the diff after it blows, is there diff fluid in there? Or did it leak out during the run?
 

DangerD

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Last Diff died with Backflip LP 6s wheels, wich are even lighter.
The Diff never leakes, not before nore after breaking.

I did rebuild it now using a fresh set of internals (gears and crosspins) and a never before used Tekno steel case (was my backup if the front plastic would break) - i did always use the same steel case for my last rebuilds. I applied some greese at the gears, filled it with 100k and added some graphite.
If this dies again idk what to do next. This is my 5th rebuild of the rear, i had spiders explode after only one pack run bye now. Tested 100k/50k and 30k oil - didnt notice any diffrence in reliability of the diff.

I dont think it is a tire issue, if so the stock plastic front diff i run unserviced since i build the truck should have died too. But for what ever reason it is always the back where spiders explode.
 
Last edited:

Jrbkeb2015

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Last Diff died with Backflip LP 6s wheels, wich are even lighter.
The Diff never leakes, not before nore after breaking.

I did rebuild it now using a fresh set of internals (gears and crosspins) and a never before used Tekno steel case (was my backup if the front plastic would break) - i did always use the same steel case for my last rebuilds. I applied some greese at the gears, filled it with 100k and added some graphite.
If this dies again idk what to do next. This is my 5th rebuild of the rear, i had spiders explode after only one pack run bye now. Tested 100k/50k and 30k oil - didnt notice any diffrence in reliability of the diff.

I dont think it is a tire issue, if so the stock plastic front diff i run unserviced since i build the truck should have died too. But for what ever reason it is always the back where spiders explode.
Hello i was wondering if you ever resolved this issue? Im having same problem but with only one run and my spider gears are shattering ive had this happen twice and only ran twice
 

FHE_nld

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Hello i was wondering if you ever resolved this issue? Im having same problem but with only one run and my spider gears are shattering ive had this happen twice and only ran twice
Turn down the punch settings a few notches maybe the setting is to high in the esc?
 

Kronuxx

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SCT410
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Last Diff died with Backflip LP 6s wheels, wich are even lighter.
The Diff never leakes, not before nore after breaking.

I did rebuild it now using a fresh set of internals (gears and crosspins) and a never before used Tekno steel case (was my backup if the front plastic would break) - i did always use the same steel case for my last rebuilds. I applied some greese at the gears, filled it with 100k and added some graphite.
If this dies again idk what to do next. This is my 5th rebuild of the rear, i had spiders explode after only one pack run bye now. Tested 100k/50k and 30k oil - didnt notice any diffrence in reliability of the diff.

I dont think it is a tire issue, if so the stock plastic front diff i run unserviced since i build the truck should have died too. But for what ever reason it is always the back where spiders explode.
Did you get that issue resolved with your rear diff?
 

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