kraton 8s keeps blowing diffs

[provokaz]

so i bought the kraton 8s exb. put a hobbywing 1100kv max5. running 30/47 gearing. 20mill center 1mill front 500k rear. finished building the car took it out for first time within 15 minutes i heard crunchy noises. took it apart sun gear and pinion had bent teeth. everyone said upgrade to aluminum diff cover so i went with vitavon. took internals out of old diff moved to new case with new sun and new pinion. within 10-15 crunchy noise came back. opened it back up could see no damage but my diff was completely locked up this time. so i took a deep dive got a vitavon bulkhead a vitavon prebuild diff case with upgraded outdrive cups and shafts. made sure all the screws were tight put it in took it out. ran for 20 minutes fine on the road. took it to my front yard before turning it off, took a small turn and gave it about 30-40% throttle coming out of the turn crunchy noise! spider gears are gone now. the original diffs i shimmed etc to no end. the new prebuilt diff with the large outdrive cups etc cant use shims they arent big enough and it honestly had zero play in the diff. i could launch this car on full throttle and the diff will be absolutely fine. take and anything more then 30% throttle my diff gives up somewhere. i've been talking to people all over facebook and nobody really has any idea's why its doing this.

ive never ever had this issue with any cars (been doing it for 10 years) i've done diffs in my savage nitro my savage flux typhoon rovan baja xmaxx list goes on. never ever had any issues i can not for the life of me figure out why this car is exploding its diffs everytime i go out and im losing my mind and my wallet at this point.

 

[SrC]

You have a fairly new rig there. And you keep throwing $mad money$ at your diff issues with negative results. Wrong approach! Just wasting coin. Those upgrade parts mean nothing for your issue. Work with the stock parts.
Could simply be user wrenching error, even though you have RC experience. Diffs in general with any RC can be a bear. There is no room for error. Shimming is important FWIW.
The 8s line is an expert level model. And with that comes expert level issues.
Sorry I cant help more. I'll let others jump in.
Good luck.

 

[Moirae]

I'm not even sure how this happens. I've never had to replace anything diff related in my arrma 8s rigs besides a bulkhead and I run a bigger motor with even more aggressive gearing. I don't know what you're doing wrong but it has to be something. Probably should start with shimming like SrC said. I never even had that problem even before I shimmed

 

[fredw90]

I'm not even sure how this happens. I've never had to replace anything diff related in my arrma 8s rigs besides a bulkhead and I run a bigger motor with even more aggressive gearing. I don't know what you're doing wrong but it has to be something. Probably should start with shimming like SrC said. I never even had that problem even before I shimmed

What shims are you using? Behind the sun gear or planetary?

 

[Moirae]

What shims are you using? Behind the sun gear or planetary?

never shimmed em, my diffs are stock. I did shim the ring gear but thats it.

 

[RC-Dude]

30/47 gearing is pretty heavy. If that's just how fast you want to drive - that's another story.

Those diffs cases are just plastic. 500k rear also really makes the diff work and creates a lot of heat. Try a 25T pinion. Thats about 15% slower and drives your Amps down even more. Go down on punch.
I just broke the internal spider gears with 24T pinion. The screws came loose on the diff lid. Rotational forces from hard braking probably do that. Only so much you can do with metal screws in a plastic diff body. Hardened loctite on the screws helps a bit but not that good for the thread. 50% bigger diffs and a stronger drivetrain would solve a lot of problems. But add a lot of weight - putting more strain on the drive train. Simply a very heavy car for plastic diff bodies.

 

[SrC]

Try lowering your Brake setting perhaps.
Very strong Brakes can do as much damage to the drivetrain as too much Punch.
Don't throttle and brake hard when landing or striking something, only use them at the moment the rig becomes composed.

 

[Moirae]

I'm geared 29/39 with 1100kv castle 2028 combo. I had rear diff screws back out once before but it never killed my diff internals. I actually think my diff screws have finally backed out again! I got that green loc-tite that works with grease to try.