Concerning the Universal Driveshafts

[WickedFog]

We just got our Granite V3 3S the other day and 5 minutes into driving it through a grass field, the passenger side rear universal came undone at the differential side. This was at 50% throttle limit too. I got it back together and we took it back out and the driverside one came loose at the axle side shortly after. I noticed both times dust and debis had gotten into the joint and was binding up the movement of the shafts.

The way these are installed, with the smaller shaft at the top, debris is making its way into the slip joint and causing this. Has anyone flipped these over so the smaller shaft connects to the axle? It seems that would keep debris from getting in the slip joint.

As a fix until new ones arrived, I put a drop of grease on the small shafts and haven't had the problem since. But the ears where the universal came apart are both damaged now, so it won't be long before these fail I am guessing.

 

[BashTillBroken]

I’m guessing your ride Height it to high you should probably limit it to a lower ride height which will solve your problems

 

[WickedFog]

I’m guessing your ride Height it to high you should probably limit it to a lower ride height which will solve your problems

I haven't adjusted the ride height. Straight out of the box. We just had another separation. But it was at 75% throttle this time. It was the universal coming out of the axle cup. The two previous times the universal separated on the driveshafts.

I will try lowering it down a bit and see if that helps. So far, we haven't had a full pack ran through this rig.

 

[Harriot10]

I see grass clippings in your rig. Heavy grass this time of year is hard on the drivetrain. Do you always run in grass?

 

[WickedFog]

Yeah, it sees some grass. Mostly dirt. I tried lowering it down and it lasted about 2 minutes before failing again (same joint - maybe overstressed). This time it was on strictly dirt. Going to put the new driveshafts in Horizon sent me and see how it goes.

Oh, note that it has never had a problem on the front.

 

[Harriot10]

Yeah, it sees some grass. Mostly dirt. I tried lowering it down and it lasted about 2 minutes before failing again (same joint - maybe overstressed). This time it was on strictly dirt. Going to put the new driveshafts in Horizon sent me and see how it goes.

Oh, note that it has never had a problem on the front.

Are you reusing the driveshafts once they fail? They’re no good once they come apart in my experience.

 

[WickedFog]

Are you reusing the driveshafts once they fail? They’re no good once they come apart in my experience.

Yes, but each time they have failed the universal joint has separated from a different set of lobes, except this last time. So next up is the new shafts, and I am going to try flipping them over.

 

[Harriot10]

Yes, but each time they have failed the universal joint has separated from a different set of lobes, except this last time. So next up is the new shafts, and I am going to try flipping them over.

Get a new set from JRC!

https://jennysrc.com/products/arrma...fts-front-rear-axle-senton-big-rock-ara4302v3

 

[Velodromed]

what he said
They’re out right now so click on the notify me and pay attention to your email because when they come in they go fast. And maybe avoid grass. Grass kills lol

 

[Harriot10]

They have some

 

[Velodromed]

They have some

View attachment 152638

Yes they do! I think I accidentally clicked on the big rock above it and didn’t notice. Glad somebody double checked

Yes they do! I think I accidentally clicked on the big rock above it and didn’t notice. Glad somebody double checked

Which is weird because I think they’re the same drive shaft as the granite. I just double checked again and yeah it’s shows big rocks out and granites in stock but I swear I thought their the same damn thing?

 

[jondilly1974]

Yep this is the Achilles heel of the 3S line. Get a set of CVDs or get yourself a 6S rig.

 

[WickedFog]

Horizon actually sent me 4 free driveshafts after I contacted tech support the first day we got it out. I normally would just bite the bullet and buy replacements, but 5 min on a brand new rig and having failures had me a bit frustrated. But yeah, I plan on getting the CVD's for the rear at least. I will try to keep my son out of the grass with it. Maybe that is the culprit. But my other rc's do fine out there

We do have a killer RC track here in town. I may try to take him there to bash a bit.

 

[WickedFog]

Yep this is the Achilles heel of the 3S line. Get a set of CVDs or get yourself a 6S rig.

Are these the ones I need? I can't really tell by the picture how these work. I assume there is a metal pin hiding in there somewhere and a retaining spring?

Or should I go for the HR ones?

 

[Harriot10]

Are these the ones I need? I can't really tell by the picture how these work. I assume there is a metal pin hiding in there somewhere and a retaining spring?

Or should I go for the HR ones?

View attachment 152689

That’s parts! Use this link for the complete CVD’s! I’ve never used the HR CVD’s, but run the Arrma ones on my BR and Granite on 4s

https://www.arrma-rc.com/part/AR310870

 

[Jerry-rigged]

Are these the ones I need? I can't really tell by the picture how these work. I assume there is a metal pin hiding in there somewhere and a retaining spring?

Or should I go for the HR ones?

View attachment 152689

that is only the slider in the middle, not the diff side or axle side of the CVD. The full set is $40 a pair. I have them, they are great. Only thing to watch for - the diff side is held on with a set screw, don't overtighten it - it is threaded in thin plastic.

That’s parts! Use this link for the complete CVD’s! I’ve never used the HR CVD’s, but run the Arrma ones on my BR and Granite on 4s

https://www.arrma-rc.com/part/AR310870

This is the correct part.

Yes they do! I think I accidentally clicked on the big rock above it and didn’t notice. Glad somebody double checked

Which is weird because I think they’re the same drive shaft as the granite. I just double checked again and yeah it’s shows big rocks out and granites in stock but I swear I thought their the same damn thing?

For V1 and V2 they were the same. For the V3 BRCC, Arrma give it wider arms, so now it uses different, wider driveshafts.
.

Last - Back to the OP - make sure your slipper is not set too tight. If it is too tight, you will break shafts more often. But, that is not always the issue. I ran my Granite on stock shafts for about a year and a half, with several different motors, including a big BLX185 on 4s. But, once I started breaking u-joints, I broke them every run - new ones, old ones, slipper loose, tight, just right, it didn't seem to matter. I added $80 of CVD's and have not had an issue since.

 

[WickedFog]

...I added $80 of CVD's and have not had an issue since.

Thanks. I have the CVD's in my cart. We have a few projects in the works right now for my son's YT channel, so will report back after we get back to this one.