Typhon and mini kraton rear diffs

[sc410]

I have been having trouble with mainly the typhon grom blx rear diff locking up on me. If I walk up to it and roll it back and forth with my hands it unlocks. I pulled the diff out and took it apart, no broken gears. The mini kraton did this to me once as well. As I indicated in my introduction post I have been on and off with RC for 15 years and have owned quite a few trucks both electric and nitro and this is my first time ever having differential issues. Any help is appreciated, thanks.

 

[CertifiedMike]

I am unfamiliar with the inner workings of a Grom but have you checked all the gears, shafts and housings for wear? Shafts straight?
Sounds like you've got something worn out thats allowing a gear shift in and out of correct alignment/mesh creating a bind/no bind condition when it rolls back and forth.

Is there any room in the diff to add shims? Shimming might help remove slop internally and smooth the gears' rotation.

 

[sc410]

I am unfamiliar with the inner workings of a Grom but have you checked all the gears, shafts and housings for wear? Shafts straight?
Sounds like you've got something worn out thats allowing a gear shift in and out of correct alignment/mesh creating a bind/no bind condition when it rolls back and forth.

Is there any room in the diff to add shims? Shimming might help remove slop internally and smooth the gears' rotation.

There isn’t anything worn or bent that I can detect. The typhon grom has only had about a dozen packs through it and the mini kraton did it at pack number 5. The steering servo also died on the 5th pack on the kraton and I am currently waiting on a response from hh about a replacement servo. I’ve only had it for a week.

I suppose shims are my only option to try to correct the issue. Thanks.

 

[CertifiedMike]

There isn’t anything worn or bent that I can detect. The typhon grom has only had about a dozen packs through it and the mini kraton did it at pack number 5. The steering servo also died on the 5th pack on the kraton and I am currently waiting on a response from hh about a replacement servo. I’ve only had it for a week.

I suppose shims are my only option to try to correct the issue. Thanks.

Good luck! I have actually heard good things about Horizons warranty program.
Shims might cure it.
I wish I had more input. I'm sure a few Grom owners will pop in soon. Maybe they know more about a specific issue to groms.

 

[RustyUs]

I don't own a Grom. Is there any known issues? I would have said a busted tooth or busted/bent pin somewhere as well. Possibly debris got lodged in somewhere and popped out without you noticing? Overextending the suspension/dog bones/CV driveshaft issue? It's easier to feel/hear things that aren't right when the motor is out of the equation. Maybe undo the pinion gear from the motor and do your rolling testing/inspection and while adding resistance to the driveline. Work your way from the wheel hexes to the diffs..... inspect every pin/bearing/screw as you go.

 

[sc410]

Good luck! I have actually heard good things about Horizons warranty program.
Shims might cure it.
I wish I had more input. I'm sure a few Grom owners will pop in soon. Maybe they know more about a specific issue to groms.

The warranty process has been slightly tedious. They have you fill out a contact form and then a few days later you get a pre-fab email asking for the same information plus pictures or video. I had already removed the dead servo so I just sent them a picture of it, not sure what else to do. It’s a dead servo. Plugging it back in and taking a video of it not doing anything would be a hassle since they have a 25MB attachment cap.

Yeah, the more I think about it, shimming is my only option. There isn’t another way I can think of to adjust the mesh and there is obviously an issue with it. It is odd that it occurs on two vehicles.

 

[sc410]

I don't own a Grom. Is there any known issues? I would have said a busted tooth or busted/bent pin somewhere as well. Possibly debris got lodged in somewhere and popped out without you noticing? Overextending the suspension/dog bones/CV driveshaft issue? It's easier to feel/hear things that aren't right when the motor is out of the equation. Maybe undo the pinion gear from the motor and do your rolling testing/inspection and while adding resistance to the driveline. Work your way from the wheel hexes to the diffs..... inspect every pin/bearing/screw as you go.

The only issues I have seen mentioned are multiple instances of unhappy people who had the steering servo die on them almost immediately. I rolled the dice on it and unfortunately that happened with mine. I’m not the kind of guy who tries to break things just to have something to fix so I haven’t been beating on these things, just driving them.

Yep, I already did a thorough inspection of the typhon and was expecting to see some carnage when I opened up the diff, but no. I did the roll test with the motor out etc. the driveline is well sealed and I didn’t find anything in there

 

[RustyUs]

The only issues I have seen mentioned are multiple instances of unhappy people who had the steering servo die on them almost immediately. I rolled the dice on it and unfortunately that happened with mine. I’m not the kind of guy who tries to break things just to have something to fix so I haven’t been beating on these things, just driving them.

Yep, I already did a thorough inspection of the typhon and was expecting to see some carnage when I opened up the diff, but no. I did the roll test with the motor out etc. the driveline is well sealed and I didn’t find anything in there

If you are pretty sure it's the rear diff locking up... swap the front and rear diffs just for amusement.

 

[sc410]

If you are pretty sure it's the rear diff locking up... swap the front and rear diffs just for amusement.

That’s a good idea, I didn’t think of that.

 

[RustyUs]

Don't they sell the internal sun/planet gears for the diffs? I didn't see the parts in the exploded view.

 

[sc410]

Don't they sell the internal sun/planet gears for the diffs? I didn't see the parts in the exploded view.

They do not at this time. They do have the complete diff for 24 bucks.

 

[sc410]

I got a reply from horizon saying they are sending me a replacement servo, no timeline or other information though.

 

[sc410]

I did some more extensive testing: regular roll test: fine, holding both front or rear tires and rolling the other two: tires lock up. Isolating just one front or back tire and rolling: fine. Holding either left or right side tires and rolling other two: fine. In other words seems to be fine. Same on typhon and mini kraton, two different setups. Mini kraton has center diff, typhon does not.

 

[sc410]

The replacement servo for the mini kraton arrived today, they were good about shipping it very quickly. Installed it and…one of the two batteries it came with refuses to charge. I’d be hard pressed to make this stuff up.

 

[danl]

My Typhon grom also has diff binding issues. It’s become my least favorite rc due to the reliability issues.

 

[sc410]

Well now they want to see cell voltages on the defective battery. These mini vehicles are my first foray into the spektrum “smart battery” system and I only have the usb chargers that came with them. My voltage checkers are the ones that use the balance plugs. Hopefully they accept a picture of the charger showing the error code(solid red light).

 

[CertifiedMike]

Is it a Spektrum charger too?

 

[sc410]

Is it a Spektrum charger too?

Yes, they are just little USB dongles that only have an indicator light. If you’re wondering if the charger itself is faulty it isn’t, the mini kraton came with two batteries and it charges the other battery as it should.

 

[CertifiedMike]

I was concerned that if you were using a different brand charger, the pic may not be enough.
They sold you this stuff... if its not enough to 'prove' their product defective, THEY should provide a tester too.

I am unsure of the quality of Spektrum mini batteries over all. Your experience is making me think the mini batteries are as bad as the rest of the stuff they sell.

RUN NOW!!!

Buy a good charger, good batteries and be done with Spekrtum's 'Smart battery' ecosystem nonsense.

I use a Hota D6 Pro charger with CNHL bats. Ovonic treated me well too.
Its not hard to operate, WAY more functional, better quality gear.

 

[sc410]

I was concerned that if you were using a different brand charger, the pic may not be enough.
They sold you this stuff... if its not enough to 'prove' their product defective, THEY should provide a tester too.

I am unsure of the quality of Spektrum mini batteries over all. Your experience is making me think the mini batteries are as bad as the rest of the stuff they sell.

RUN NOW!!!

Buy a good charger, good batteries and be done with Spekrtum's 'Smart battery' ecosystem nonsense.

I use a Hota D6 Pro charger with CNHL bats. Ovonic treated me well too.
Its not hard to operate, WAY more functional, better quality gear.

It seems to me they just have QC issues across the board. I like their designs and if the smart batteries worked then ok. But over the years I’ve never had this amount of problems over all different aspects with any other manufacturer to include traxxas, HPI, losi, etc. Dead servos, dead batteries, drivetrain issues, all after a comically short amount of use/ownership and neither truck has been more than two feet off the ground…